Hmm, how are you finding the speeds/reception with the XXKK6 radio? I flashed to it briefly but it seemed to be worse than the stock UGKL1. Didn't play with it enough though.
The XXKK6 radio is a European radio, so logically UGKL1 should be better to use in Canada right? Otherwise they would have just kept it at the stock radio.
Here's a list of all the basebands btw:
[Radio] (GSM) Galaxy Nexus I9250 Baseband dumps collection & discussion - xda-developers
If you're having problems with XXKK6 you can flash back to UGKL1