From Digital Spy's Tube Talk Q&A section:

DIARMUID Bulanda-Dineen: "Hi, just wondered if you could let us know when Rescue Me Season 4 will be airing in the UK, thanks."

Neil: In a shock twist, I've been told that Sky One has decided not to take the fourth season of Rescue Me. Furthermore, I hear that the next logical broadcaster in line has also passed on the show, leaving this quality series homeless in the UK! Outrageous, no?