I have played in a few of these - Bolton Wanderers, Blackburn Rovers, Manchester City, Ipswich Town and Scotland (even managed to score at Hampden). It is a great idea but it is usually only EPL, Championship and SPL teams that are involved though not all of them as the facilities have to be available for use when the games are being played and importantly the club needs to want to do it.
When ICT were in the SPL there was a hope that a game at TCS could be a possibility. There was at least one thread on it as well as the possibility of a game being raised with the club through the boardroom banter facility. The club asked for further details to be forwarded but it never got any further than that unfortunately.
I still get all the Football Aid e-mails and I notice that this year there have been a lot of unsold positions - usually there are very few and they are usually 45 min slots. Currently there are still open positions at more than 10 clubs including both games at Anfield which is usually one of the first to be sold out very quickly. I assume a lot has to do with the current financial situation in the UK so getting 28 people to be willing to play (and pay for) a Football Aid game at TCS and getting the club to want to do it might be a while off yet.