I think these cities reflect the semifinalist interviews. So perhaps the contestant locations reflect the cities chosen.
Why don't y'all look at last season's cities visited and see if it matches up with the racers.
So the interested fan in me took some time out to dig through Twitter posts from last year of Mike, Mike and Mark to see if there were similarities between where they were and where the contestants from S.4 were from. It looks like on Dec. 10 they were in Delta BC, in Dec. 14 they were in Regina, Dec. 17 Toronto, Jan. 9 in Westmount, QC and Jan. 14 in Vancouver. Of course some of these posts could simply be personal travel too.
Also interesting, the racers weren't revealed to the staff at Insight until March 28 (Mike Bickerton's post). Seems like they deliberate a LONG time on things. Perhaps arranging background/health/visas/insurances/notifying employers/last minute changes/etc.
If this is accurate and holds true again this year, I suspect that they will have completed their interviews by the end of this week and will begin the deliberations.