The trade comes one day after Cammalleri questioned the Canadiens' attitude in the dressing room after a loss to the St. Louis Blues, and said the team played with a losing mentality.
Montreal's general manager Pierre Gauthier denied the trade had anything to do with the recent controversy and said the team has been working on a deal for more than a month.
"No, not at all," Gauthier said. "I didn't make a big deal about all that. There's emotion around the team, somebody says something, I'd rather see emotion than people that don't care. ... He never asked to be traded or anything. He's part of the team and he cares a lot. That's why he made those comments."
Cammalleri, a native of Richmond Hill, Ont., has nine goals and 13 assists for 22 points in 37 games for the Canadiens this season.
Calgary also acquired goaltender Karri Ramo and a fifth-round pick in the 2012 draft.
The Canadiens received forwards Rene Bourque and Patrick Holland and a second-round pick in the 2013 draft. Bourque is currently serving a five-game suspension for elbowing Washington's Nicklas Backstrom in the head.
"I wish him nothing but the best, I hope he goes (to Montreal) and has great success there," Flames coach Brent Sutter said of Bourque.
Gauthier said the young players who joined the team this year like David Desharnais and Rafael Diaz are smaller skaters, but the team needs to get bigger.
"The majority of goals are scored around the net now, on deflections, screened shots," he said. "We need to score those difficult goals. You need to go to those areas to get those second and third chances."
"We improved our team tonight. It's not to put down Mr. Cammalleri, it was to get bigger as a team."
Cammalleri is listed as five-foot-nine and 190 pounds, while Bourque's player profile says he is six-foot-two and 211 pounds.
Cammalleri returns to the Flames, where he had 39 goals and 82 points in the 2008-09 season, both career highs. The trade shows the Flames are serious about contending for a playoff spot. Calgary is hoping that Cammalleri can quickly find the chemistry he once had with former linemate Jarome Iginla, the Flames' superstar captain.
"We had good chemistry. He has a knack to get open and get a one-timer. But he's not just a shooter too. He's able to make passes and get points and produce. I know he enjoyed playing here. The fans liked him and he liked Calgary.
"You felt like anywhere you passed it around, he could get it off and and get it on net. That’s one of his biggest strengths. Power play but also just able to get open."
Calgary is 12th in the Western Conference, but only three points behind Los Angeles and Minnesota for a playoff spot after a 1-0 overtime win over Anaheim on Thursday.
"We think he's a dynamic player," Calgary GM Jay Feaster said during the first intermission of Calgary's game with Anaheim. "He's a player who has had success here. He's a player who is familiar with a lot of players in that room.
"We feel he helps us on the power play, which is an area where if we're going to make a run here in the second half, we need the power play to be very good. From our perspective, he's a guy that needs a change of scenery right now."
Bourque, who has 13 goals and three assists in 38 games this season, said the move took him by surprise.
"It's a big shock. I had no idea that any of this was going on," he said. "But, if there's any place I want to play, it's Montreal. I've always enjoyed playing there so I'm happy that I get to go to a place where I enjoy playing.
"I spent 3 1/2 years here. I'm going to miss the guys, the staff, and everybody that’s involved in the organization. But, I'm going to a new family now."
Although Calgary and Montreal had been in negotiations for some time, things came together quickly on Wednesday.
"When Bourquie was suspended this most recent time, I thought there no sense trying to advance it any further while he was on the suspended list," Feaster said. "Last night, Pierre called and asked if we were still interested and I said we were, and we started working on it again last night and into today and ultimately got it done late this afternoon."
Montreal coach Randy Cunneyworth confirmed the deal after Thursday night's game against Boston. Cammalleri was pulled during the third-period of the game and apparently sent back to the team hotel.
Cunneyworth said he was told to keep him out of the lineup to avoid an injury that might jeopardize the deal.
"It's just something that is not too common during a game, but he was pulled away from the ice and obviously been dealt," Cunneyworth said. "The only message is that we're trying to improve our team. Obviously, a general manager makes a deal only if he feels he's strengthening the team. We feel that will be the case. That's the only motive and we feel strongly about that."
So far, this has been a season to forget for the proud Canadiens franchise. After stumbling out of the gates, the team fired head coach Jacques Martin. Cunneyworth, Martin's replacement, sparked controversy when it was revealed he couldn't speak French.
"I might be in trouble too, I don't speak French and probably have the most French name on that team," Bourque joked. "I know a few words, but that's just from school."
The Habs are languishing in 12th place in the Eastern Conference, seven points out of a playoff spot.
Feaster said Cammalleri is already relishing his first game back with the Flames.
"When I phoned him, and I said who it was calling, the first thing out of his mouth was: 'What are we, four points back? Saturday night, it’s the Kings right? Hockey Night in Canada.'
"He told me he can't wait to get here."
— With files from Darren Haynes in Calgary and The Associated Press.