It will depend who you talk to there. I got them to unlock one mapset to both my 276 and 478. A no-no, but I convinced
If your Lifetime maps are unlocked already to another unit, I doubt they will transfer them to another untit you just bought. Technicly, they are lifetime updates to the unit it is originaly married to.
As stated above, the only time they will transfer the unlock is from a Garmin repair/exchange. In fact I just did this 3 weeks ago. 2013.3 on my "newly refurbed" Garmin sent back.
Now registering the unit you just bought. My buddie bought one somewhere that was already registered. Garmin would not register it. He had to contact the registered owner. They have to release the registration. Garmin would not.
Another case of "who you talk to at Garmin"