If you think flying from Toronto Island Airport amounts to significantly lower taxes on flights, think again.  The total costs added to any airline ticket, be it from Pearson or the Toronto Island Airport, add a significant weight to the costs of travel.
 
These are the taxes a passenger will pay for a ONE-WAY Porter flight from the Island Airport to Montreal.

$  4.67 CAD   ATSC - Air Travellers Security Charge
$58.00 CAD   NAV and Surcharges
$ 15.00 CAD   Airport Improvement Fee
$  8.33 CAD   GST
$86.00 CAD   Total Tax & Fees

Taxes on round-trip flights from the Toronto Island Airport to Montreal total in the range from $154 - $174

By contrast, a ROUND-TRIP ticket on a VIA train costs a little as $153.30.

IN MANY CASES THE TOTAL COST OF A TRAIN TICKET TO MONTREAL IS LESS THAN THE
TOTAL TAXES ON A PORTER FLIGHT!!

Just another reason why you should take the train...