I am not sure when exactly this happened but RIM really snuck this one in. We saw that RIM published the documentation for BIS 3.1 but we did not hear much from the rumor mill about its rollout. Thomas pointed out to me that Yahoo email accounts connected to the BlackBerry BIS service now have the option for wireless contact sync which will synchronize your Yahoo address book wirelessly with your BlackBerry.
This Yahoo contact sync was one of the main features in the BIS 3.1 upgrade so its great to see it live. If we truly are on BIS 3.1 it should also sync contacts with Alt-N MDaemon v11 over SyncML. It should also have an improved change device update but I don’t have a device I need to change into to try it out on.
Let us know if you try using the contact sync for Yahoo and if it works for you!