I don't think it is necessary to have it on hand for that reason because quite often a mothers milk wouldn't have even come in before she left hospital anyway, even one that continues breastfeeding. Obviously they would need something for 'emergencies', such as really prem babies, but then again (in IMO) it would be ideal if hospitals had their own milk banks where donated breast milk could be used in emergencies. If a mother is planning on not bf, then she should be responsible for organising her own bottles and formula(IMO) because I believe that the nurses have a duty of care to that baby which includes supporting and encouraging the mother to breastfeed.
I think its necessary to have it on hand... If you know is advance you are bottle feeding, its up to the hospital to decide if they will provide it or not, the same as if they provide nappies, but there have been cases of medical emergencies afterwards where women are either in extensive surgery or something a lot worse and aren't around to breastfeed. I would think the hospital has a higher duty of care to provide formula, than to give milk from a milk bank without express permission of the parents, as some people are not comfortable with that, just as some people refuse to have injections that are from blood products etc (either blood transfusions, anti-D).

I support b/f, but i also think its the parents right to choose what they feel is right for their child for whatever reasons, just because the hospital is a pro-b/f hospital does not mean that the have the right to choose for those parents.