I would imagine the "getting there" but also falls under the responsibility of the local authority as well to be fair to the club, not that it should give them an easy out.
I cant imagine that it would cost that much in the greater scheme of all the money that's chucked around in the game these days, to sort something out? its a big site, there must be somewhere they can put aside for disabled parking? even if it can be right next to the stadium, get a couple of golf carts and a couple of stewards on to drive them?
(I have no idea if that would help but in my head it would)