I am not aware of a single online MBB being "target school" for MBB. Other consultancies may accept them, but probably only rarely. Besides the lack of brand name, your main difficulty will be overcoming the common perception that online degrees are watered down and you just need to pay to get the piece of paper. Shaquille O'Neal got an MBA from the Phoenix University, but I don't know anyone who thinks of him as a real MBA.
I think your best bet is to find someone who did an evening or executive MBA, and who will understand how hard it is to actually pursue graduate studies while holding a full time job. I did it, I know it is not easy. But even I still don't view online MBAs are 'the real thing'.
My advice to you: if you want to join MBB or even a strong Tier2 consultancy... do a regular program