A is the top floor of the parking garage. 2 stairwells, an elevator, and ramp entry. Fairly easy to cover from behind the north stairwell. Zipline entry is limited to the roof of the bank. You get spotted pretty quickly from A when you're up there. Try to zipline and I'll shoot you and melee it away.
B isn't vulnerable through the subway at all. All the Subway exits are far enough away that you can get mowed down before you get close to capping. Police send the bag back and GG. Zipline in? Tripmines on the bus will kill you as soon as you land. For added giggles, I'll prone behind the subway entrance in front of B and pick off anyone trying to rush the cap.
C is only easy to cap if you're quick enough. But that's why I specifically cover C as soon as the game starts. Camera on the road to Thief spawn, tripmines in the kitchen to drop anyone trying to run from the vault wall and a 240Bravo pick up if I need to put a bunch of bullets downrange to suppress a surge of Thieves. Hang in the outdoor hallway behind the ledges with the hedges and pick people off. Use the columns to prevent roof snipers from taking you out.
Any of these points can be taken easily but when people use cover and tactics, it becomes much, much harder.
Any of these points can be capped quickly but
Well I definitely snipe off everyone from the top of A before I zipline in. And if the top of A is hot, I go down the stairs and go into the middle sections of A through the bank windows. Stairs are very vulnerable from the side as they are open windows, and even the north of stairs is easy pickings coming from the driveway ramp.
B is definitely the hardest, but I had most success with the subway. It confuses the cops and force them to go down, then the other robbers close into B from the top and spawn camp. Funny thing about tripmines on B is that I spot them before laying down ziplines. I've actually gotten B with 5 tripmines there. Pick a nice spot, zip down when it looks like robbers are successful, plant my beacon, and stay alive. If the B bus area is too hot, I'll just snipe off easy targets and chute down to the subway.
C is easy for me because I always win the kitchen. ALWAYS! I've killed 4 guys at the intial confrontation because robbers always get there first to get better... ahem...
cover. And my beacon is there all the time, so even if I die, I spawn and surprise them.