Polis Massa is a medical facility on an asteroid, as seen briefly at the end of Star Wars Episode III. The main feature on this map is the uniqueness of having a kind of "no mans, vehicle only land" in the centre. This tank battle usually doesn't affect the battle when playing with the AI, as they only attack enemy tanks, rather than dock in other hangers.
However, one good strategy a the CIS is quite simple. Walk outside. As you re a robot, and don't require oxygen, you won't lose health. Use this as a droideka to flank an enemy, or as an assault droid for easy picks on tanks.
Avoid the two corridors between the 3 and 4, especially if you are defending. The corridors are FULL of attackers, and counter attacks are difficult. There's a reason why CP 3 is contested so often. Mines, detpacks and grenades cause heavy casualties. Avoid the bloodbath when defending, and instead focus on attrition. Grind down their forces with explosives, and only launch a counter attack when lead by a hero, or when there are certainly only few enemies remaining. Even then, respawning enemies won't make it easy for you. If you manage to capture and hold both CPs on each end of the corridor, expect the battle to be more conventional.
As the Empire, get in a tank by the forward command post as either a sniper or a stormtroper. Ignoring the rebel tanks, enter the hanger at the other end of the map, by the rebel CP. Capture that CP, keeping a lookout for snipers, and proceede to the rebel CP away from the two tunnels, eliminating all resistance. Continue to move back towards the first CP you spawned at, capuring CP's and killing rebels.