Buying US-registered bike in Uruguay, will have title, can I leave with it?

[SenorBoludo]

I've been searching for the past 5 hours and haven't found the answer to my specific question (googling with site:horizonsunlimited and a variety of search terms), so hopefully someone who has done this can help. There seems to be a ton of information about Argentina, Peru, Chile, but almost none about Uruguay.

I have a friend who has a US registered bike in Montevideo that I'm going to buy. He's in Colombia now and won't be in Uruguay when I pick up the bike. Before I leave the states, I'm going to get the title transferred to my name, and registered in my name (I know there is some dispute about whether this is possible, I've done it personally before, have spoken on the phone to the dmv to verify, and am 100% certain I will have title, reg, bill of sale, and plates in hand when I leave). The bike right now is on temporary import papers in his name.

Does he need to be there when I leave the country with his bike? Can I just put the new plates on and leave the country, canceling his import papers at the border and entering argentina on my new papers? Or do I need to leave the country with the bike still on his plates and title, and change everything on the ferry to BA?

If I need to leave the country on his plates, will a simple poder allow me to do that, even if the old title and reg are no longer legally valid? Also, I'll need to surrender the original title when I change the title here, so i'd only have a photocopy of the old (his) title.

Anyone successfully transferred ownership of a foreign bike in uruguay (or anyone else) know the answers?

Thanks in advance...