I don't think an all vegan bakery is going to work here. Vegan options sure, but you're really catering to a small customer base.
I think if it is cute enough and offers interesting and yummy baked goods it could do really well. I don't know that all people who stop in will know it is particularly vegan friendly (unlike places like V Spot where it is in the title) and it would be near the G train and get some morning traffic.
I believe Dun Well doughnuts is doing well (!), likely because of location near a train and offering really interesting and yummy foods. Over the holiday I stopped in for a chocolate peppermint cake doughnut that tasted like xmas!
I think to be successful this bakery will have to appeal to vegan and non vegan alike, and convenience, uniqueness, and quality will all be important. I haven't had a chance to try it yet, but if nothing else maybe this weekend.