Carlton.com wasn't exactly much different. It was a commercial portal made up of other businesses in the Carlton group such as Popcorn.co.uk and Jamba.
I think they were even criticised after rebranding and at some point had to change the url to www.carlton.com/tv
which pointed to something more relevant to its ITV activities. (That's from memory... I may be wrong!)
You're probably right as the same happened to Granada with their G-Wizz Promotion on idents.
In 2001, the whole charade ended in November 2001, when all ITV regions adopted the ITV.com URL (not all at the same time, I should add). Oh, and by the way, Carlton changed their URL on 27th November 2000.
This is Carlton Television - Part of the ITV Network. Now at 11 O'Clock, Time for the ITV Nightly News from ITN.