My favourite batt map so far. Though i'm not sure about the large ammo and health at last. You should probably split the ammo into two mediums and place them on either side of the track so engi's can setup at more positions. It would also be sensible to split the health into 2 smalls and have them accompany both ammo packs (as seen in goldrush).
The long flank around the back of last goes largely unnoticed; for the 40 minutes we played i used it once at the very end. It should at least be a lot more noticable for BLU as currently the most obvious access point to this flank also looks like a death ledge, not a drop down.
The first corner past CP3 is sort of a large choke for BLU, they don't have sufficient opportunities to flank RED here as even if you climb the boxes to get onto the stone catwalk RED can see you do this and snipe you, or intercept/ambush you at the other end of the building you pass through in order to progress forwards.
I'm not a massive fan of how small the starting area is, but then that's not 100% your fault, but the track design. What exacerbates the claustrophobic feel though are the really high walls that also subsequently cause some large shadows. All of my deaths in the starting area (all be it 2 or 3) were because i got confused and started shooting an ally in the shadows and got picked off by an actual enemy somewhere else.
Putting a roll back zone on the starting slope should help balance the fact that the starting area is pretty much a BLU steamroll; and give RED more incentive to counter-assault.