I would imagine that as with nearly any game, there would not be some arbitrary hard-coded limit to the number of polygons. Limits would be imposed merely by how well the engine can render everything on screen at once, a soft limit depending largely on the player's hardware. The only thing you can do now is test your models in SF or email Malfador, as anything more specific would be covered by NDA.
Aside from which, the single-ship poly count isn't really the core issue...
The total on-screen poly count when you're playing CarrierBattles, and have 2000 fighters and 150 warships slugging it out is what will really stress the system