why didn't you take the deal......(spoilers)

just before, or during, the final showdown, Masters asks Vukovic (probably spelled wrong I know) "why didn't you take the deal Grimes offered you? Wouldn't roll over on your partner huh?"
So are we to take it from that that Masters knew about their operation all along? If so, why did he go along with it and allow himself to get caught?
I can only guess he knew the net was closing in, and therefore it was better to be busted by a shoddy operation that his lawyer could have him beat all day long. Back then you couldn't be tried for the same crime twice so they'd have to back off after that. But that still doesn't explain why he was getting his girlfriend to look through their car when he met them at the gym etc, unless he was seeing what he was up against and how thorough they were.
Or it could simply be part of his death wish/thrill seeking.