Gal Gadot, Michael B Jordan, Teresa Palmer, Michael Pena and Aaron Paul are also in line for the film, reported Variety.
Casey Affleck and Chiwetel Ejiofor have already signed on for the movie, which centres around a Los Angeles heist.
A group of corrupt cops plan to murder one of their colleagues in order to distract the authorities from the robbery across town.
'999' is police code for 'officer down'.
Winslet can currently be seen with Josh Brolin in 'Labor Day' and will next appear in young adult novel adaptation 'Divergent'.