IMHO the Brits just want him out of their prison system. I reference this quote from the article:
“Prison officers have warned of the threat of extremists “radicalising” inmates.”
“Prison officers have warned of the threat of extremists “radicalising” inmates.”
I have no doubt that our British Friends would be delighted to be rid of him for the reason you cite as well as the fact that he has been an extremely "high maintenance" inmate....just search Free Republic or international news sources with keywords "abu hamza" and you'll get a bushel basket of hits, all detailing some effort on his part to manipulate the system in one fashion or another.
He also continues to have a strong following in the UK and it will be good for overall security there to be rid of him so that he will provide less of an inspiration to empty-headed jihadists.