Hmmm, Lucas went to the PRCU from 1995-1999, which is probably not useful for anyone else. But since that time, he has been part of a few efforts H.E.L.P. has made towards research, development, and the occasional protection/enforcement. So, anyone who's kept up ties with H.E.L.P. might have a small history of acquaintanceship with him, provided they've been to Canada.... And anyone else they'd have had to have crossed paths within the last year.

It's possible, though probably rather far-fetched, that he might have come across memories of some individuals while traveling, Zeke being one of them, as the first direction Lucas went was cross Canada then down. If he did encounter Emory either physically or through a memory, he'd probably remember it and make much of any re-encounter. Simply because His Sliminess is an extremely strange phenomenon as far as he's concerned.

Gareth, he has probably never met at all, despite proximity. 

Not sure about Marcus or Ilani.