I use Shell V-Power up here in Ontario which is readily available along most highway stations and in the burbs. Not so available in downtown Toronto.
The actual cetane value is never listed anywhere but I saw a thread once where someone e-mailed head office to find an answer. I've used both and my car is a CPO and I can easily say that the premium diesel made a noticible difference for my car especially for starts from a standstill. There is significantly less turbo lag and engine noise.
The price difference up here is 5cents/l compared to regular diesel.