It’s been brought to my attention (thanks Brent!), that with a slight modification of the new iSync, Telus (and maybe other Canadian carriers’) phones can be fully supported. Edit the Verizon version of the V3c in the iSync MetaClasses.plist file such that “supportsCalendarsSync” is set to “yes”, that’s it.
I’ll be updating the plugin page soon to include relevant information now that the new version of iSync is available.