as far as i know, NOM's ex had his vasectomy reversal done on the NHS, so it is possible. It's probably case fact dependent though - ie he was with a woman who didn't have any kids already,(whereas in this case he has simply changed his mind, and is still with the mother of his other 2 kids)
I wonder though, if the fact it's a fairly major procedure might put him off?
I know that you haven't asked for people's advice, just facts but you/he needs to consider that it's best not to get pregnant while on the medications you are on, but being off them might cause PRE natal depression