I don't know specifically which ONE model the OP has, but from what I can tell on the TomTom web site, none of the ONE series support bluetooth. If that's the case, that would explain why there is no "Mobile Phone" icon on the main menu.
Regarding another question, you can't use a compatible phone as a substitute for the RDS-TMC receiver. You CAN use a compatible phone to get traffic updates using TomTom Traffic, but this is different, and requires a subscription DIFFERENT than the subscription required for the TMC receiver.
I was able to get a free year of TomTom Traffic by calling TomTom and asking for a free trial of TomTom traffic because the TMC receiver didn't get any reception in my area. You could try this also, but there's no guarantee that they would do this for you.
Also, there are many phones that work which aren't listed as "supported". I would imagine that the N95 would work fine. One way to know for sure would be to take your phone to a retail store and pair it with a display model, then try to use the weather service under TomTom Services. Supported phones can be setup quite easily, whereas others may require quite a bit of information because you have to provide a lot of the details manually. It would be best to check sticky in the "tweaks" sub-forum for as many details as you can get regarding your phone model and carrier before heading out to the store to test for yourself.