You can win on that map if you push and work as a unit somewhat. If you are just going in 1 or 2 at a time it'll be hard. Now if they have 2 bastions and 2 turrets (like my match last night) you aren't going to win easily.
As for wiping them and they return? Simple. You wipe them and have explosives, turrets and stuff pointed at their spawns. Same thing happens on Gibralter at the final push