Engy, if you click the 'friends' icon up top in uPlay interface, then click "+Add Friends," the resulting pop-up window has a blue "Import Friends from Steam" button. I'm not certain what it does; I assumed it would add Steam friends IF they're on uPlay too, duno for sure.
Ooh, neato! I hit that button and it did come up with a big list of people on my Steam list that also have a Uplay name that I could add. Mass invites sent, haha!
As far as account linking goes, I thought that was more a function used so that if if you bought a game via Steam but play it actually through uPlay (a la The Division), then uPlay automatically would launch when starting the game from Steam. If that's not too confusing.
And of course I could be wrong. The whole "buy a game on one service to play it on a different service" makes my head spin.
Aah yeah, you're probably right about that. Duh, didn't even occur to me.