I prefer lockers to metro though as there are several routes you can try if one is really bottlenecked, unlike metro which had red stairs then front and back escalators...that was all the choice you had really...and they are all right next to each other....at least lockers has upstairs routes, downstairs and outside routes to try and sneak/push/flank.
all that said.... still completely possible to get spawn locked...had a silly fast round on lockers 2 nights ago...was over in what felt like 10 mins sure it was 800 ticket too xD
little tip for locker mortars
oh my its funny as hell in some game types on there they at bottom rush out to snow hammer mortars straight on them. on some maps ive had like 20-30 kills in like 3 or 4 minutes doing this
also if they get trapped its like mortaring fish in a barrel.