Actually, it isn't just RSPCA that shut for X MAs, pretty much all rescues do - we stop homing for X Mas in a fortnight, and officially we dont take any in, although that hasn't worked the last two years. You can't actually get hold of my CP Branch after a certain date in December, they just keep the phone on answermachine. There are very valid reasons for not homign over X MAs, and if you are full on the day you stop homing, you can't take any more in.
My fosters tend to be with me an average of 3 months CC, but at least she will be going to a home environment rather than a pen, so she should be fine. Not sure why your friend can't just keep them as indoor only cats though, if the road is an issue.