Its all about a common demoninator.
There are type ratings and there are type ratings. easyJets training is second to none, its one area they never scrimp and scrape on. By sending their pilots through their course they know what they are getting and to what level they have been trained.
All in all its a good deal for everyone except easy's pockets!
You wont be 'reissused' with a new rating, if its on your licence you keep it. The CAA would be more than happy to reissuse you with a new rating - after all its another fee for them!!