Guess you wont really know until you get the cable. I am basing my views on what is in the US, I think the cable has a custom connector for the ipod, but I may be wrong. I'll see what I can dig out with respect to it, I have the US sat nav manual somewhere.
I fully agree about the 2010 upgrade, I held off ordering mine especially for that. Nissan dealers didnt know anything about it either, it was announced in the roadster launch, I only knew of it by reading forums in the US. To be fair to WLMG in Slough, they did chase NMGB up to ask them the questions about it though and I finally got put in touch with the Nissan product manager for sports cars.
EDIT: Done a bit more reading on the US forums, and sorry to be the bearer of bad news, but I think your dealer is right, iPod can be connected to the system, but no integration, have to control it via the ipod. In the US they got integration before the 2010 update, but it appears outside of the US/Japan it doesnt work (confirmed by a chap in Oz)