The 767 is a classic old-school Boeing, durable and long-lived.
There's a reason that so many retired 767 airliners were converted to freighters.
AC obviously feels that they need these passengers frames back in service now and I'm quite sure they've done their maths on the coast versus the benefit.
I'd also bet that these are among the lower hours and cycle birds AC parked and have no damage or corrosion history, so are well suited to return to service.
Quite a few aircraft that it was planned would never fly again have been returned to service in recent years, since new build deliveries have been slow and traffic growth has exploded.
I'll add that the 767 is any coach passenger's first choice with 2-3-2 seating to go with two aisles.
They are nice to fly in.