BAR team boss David Richards will leave at the end of the year after engine provider Honda agreed to buy a 45% stake in the Formula One team.
Honda has supplied engines to BAR for four years and is keen to increase their involvement in F1, as BBC Sport exclusively revealed on Wednesday.
It has agreed to buy a minority stake in the team for a substantial sum and started a management shake-up.
Richards guided BAR to second place in last season's championship.
BAR's parent company British American Tobacco (BAT) will now form a joint venture company with Honda which will replace the existing structure, with BAT retaining a controlling 55% stake.
Richards - who successfully blocked star driver Jenson Button's attempt to move to rivals Williams earlier this year - has been ousted a year before the end of his contract as a result of the reshuffle, but he remains positive.
"We were brought in by British American Tobacco to turn the team around and secure its long-term future and that is what we have done," said Richards, whose Prodrive organisation also challenges for international titles in rallying and sportscars.
"I am immensely proud of what Prodrive has achieved in a shorter time than anticipated.
"I believe that BAR Honda is now in a very healthy position to continue its pursuit of the world championship."
Richards, 52, will stay in a consultancy role until the end of February.
Honda managing director Takanobu Ito added: "This is a natural extension of our relationship with BAR and is an important step for both partners.
"The new commitment will further strengthen the structure for cooperation as we push forward with our Formula One challenge."
BAR were the surprise package of the 2004 season, with Button often the only rival to the dominant Ferrari drivers and helping the team to a second-place finish in the constructor championship.
However, despite the Briton finishing second four times, BAR have still yet to win a race.
The team was formed in 1997 by Craig Pollock, Reynard Racing Cars and British American Tobacco, which provided the bulk of the financing.
After buying the Tyrrell team, they made their Formula One debut in 1999.
As part of the deal, BAT and Honda have made an offer to buy the small 10% stake still owned by Pollock, and then-Reynard bosses Adrian Reynard and Rick Gorne.
BAT says if the shareholders refuse to sell, it will seek the appointment of administrators to the new holding company.
"The new joint venture company then expects to acquire, from the administrator, the shares in British American Racing GP Ltd which operates the team and which is the holding company's principal asset," said a BAT statement.
"The day to day activities of the team will not be affected
by this process."
Honda will appoint directors to the board of BAR and add a number of staff to the 30 engineers at the team's Brackley headquarters.
BAT is thought to be scaling back their interest in F1 because of a law which bans tobacco advertising from mid-2005 with a worldwide ban due to be enforced by the end of 2006.