The automaker is deploying miniature remote-controlled versions of the car to move track and field equipment around the Olympic Stadium.
The IOC's in-house broadcaster has regularly zoomed in on the radio-controlled cars and sent images to networks around the world, giving BMW global exposure of its brand.
The IOC's television and marketing director, Timo Lumme, said at a news conference that the rules weren't being breached because the cars don't feature any branding.
But the phrase "it's a MINI adventure," is printed on the cars and Lumme later acknowledged that from "the silhouette ... you can recognize it's a Mini."
"There are a number of IAAF validated vehicles that could have been used," Lumme said, referring to track and field's governing body. "So the one that they chose, quite naturally, because BMW is the sponsor, was the BMW one."
As a top sponsor of the London Games, BMW's sponsorship is worth 40 million pounds ($63 million), which includes the cost of providing vehicles.
Rule 50 of the International Olympic Committee charter states that "commercial installations and advertising signs shall not be allowed in the stadia."
Olympic sponsor Omega has its logo on clocks in venues, but BMW has specifically used its Mini for a task that could have been carried out by a generic vehicle.
"We are obviously pleased with the result," BMW spokesman Graham Biggs said. "The Mini shape is recognizable — it's all about good design. They are not branded but the design is something people recognize as Mini."
Biggs insisted that the Minis, which collect javelins, hammers and discuses and return them to competitors, adhere to the rules.
"This is something that was discussed at length with LOCOG and the IOC," he said.
BMW acquired the Mini brand through its 1994 purchase of the Rover Group. Conceived as a thrifty vehicle during the 1950s fuel crisis, the car came to symbolize fashionable Britain of the "Swinging Sixties."
BMW's canny use of Minis highlights the challenge sponsors face at the Olympics to secure a return on their investment when exposure is heavily restricted by the IOC.
Steve Martin, chief executive of marketing agency M&C Saatchi Sport and Entertainment, said the use of Minis is the "surprise sponsorship of the Olympic Games."
"People in the industry will look and see it's the smartest thing around the Olympic Games for a long time," Martin said. "The Olympic Stadium is almost a brandless sanctuary within the Olympic Park."
Martin said it is akin to a marketing ambush because of how the cars have been woven into the sporting action.
"Within the sponsorship industry it's hit the mark which is rare," he said. "I'm looking at it and wished we'd thought of it. I actually think it's something that a lot of brands would have given their eye teeth for."
But the Minis could open the floodgates at future Olympics for sponsors to search for ways to bend the IOC advertising restrictions.
"Fans have become accustomed to seeing their favourite Olympians in clean stadiums but they may come to accept brands appearing on the field of play if they have a clear role and add some value to the experience," said Lucien Boyer, chief executive of brand agency Havas Sports & Entertainment. "The Mini radio control cars collecting javelins have been useful to the organizers and amusing for spectators.
"However, the IOC must be sensitive to the reactions of other partners and mindful of what has made their sponsorship program so successful as these opportunities develop."