Montoya is six points behind his team-mate in the title chase and Williams are just three adrift of Ferrari in the constructors' table, but Williams are playing down the prospect of a title challenge.
The bonus point was sealed just before the break when referee Tim Hayes awarded a penalty try for an obstruction by Darren Cave on Ugo Monye and Brown continued the scoring after half-time after winning the chase to a Williams kick.
"We're going to have a long talk about Mike's future - whether he wants to go to retirement or whether we'll chase a rematch with Williams, " said Tyson's trainer Freddie Roach.