The illegals in question are Portuguese construction workers, mostly visa overstayers, who came by plane. (Canada's Southern Border is famously undefended, but they don't need to build walls to keep Americans out.)
The Liberal government would have let them stay.
Early last year, then-Immigration Minister Joe Volpe said he would try to find a way to get legal status for undocumented workers.
"They are here already and have proven themselves to be integrated," Volpe said at the time. [Tories begin deporting illegal workers|Portuguese families caught in immigration crackdown, by Peter Gorrie, Toronto Star, March 21, 2006]
Mr. Volpe's motives for this amnesty may have been pure, but there's a simple political equation in Canadian politics: One Portuguese immigrant=One Liberal vote.