If Bucky is in WS mode then he can keep BP busy or maybe give him a hard time. Meanwhile since Tony doesn't have flight or Fight analysers or even repulsors, It would be a Cakewalk for Cap to dismantle his mask or weak points in his armour or just disable his Arc Reactor after just a couple of hits with his shield. Even without his shield Cap can defeat him since its evident Tony is very very inferior to Cap in H2H as Friday stated. It's just a matter of time how long Cap takes to defeat Tony and then Together they will crush BP. Hell Cap was taking on War Machine and BP simultaneously for a few moments and managed to kick War Machine out of the sky with a flip kick and then quickly put another roundhouse kick on Panther and pushed him couple of feet.
Give Tony the fight analyser and Tony and BP will take it almost every time.