Via's web site gave me the following luggage restrictions.
BAGGAGE ALLOWANCE (VIA)
One (1) personal article of up to 11.5 kg (25 lb.) / 43 x 15 x 33 cm (17 x 6 x 13 in.)
One (1) large article of up to 18 kg (40 lb.) / 158 linear cm (62 linear in.)
Two (2) small articles of up to 11.5 kg (25 lb.) / 54.5 x 39.5 x 23 cm (21.5 x 15.5 x 9 in.) each.
OVERWEIGHT CARRY-ON BAGGAGE:
Additional fee of $20 tax incl. (per one-way trip) if baggage is 18.5-23 kg (41-50 lb.)
Carry-on baggage over 23 kg (50 lb.) is not permitted on board.
ADDITIONAL CARRY-ON ITEM(S) ALLOWED:
One (1) additional article of up to 23 kg (50 lb.) for a fee of $30 tax incl. (per one-way trip).
How strict is Via on the dimensions? Are rigid sizing boxes used to determine if an object is oversize?
The pay-per-item fees listed address weight but not size. Are oversize items allowed at all?
In case it matters, I would be taking the Maple Leaf to Toronto and the bus from Toronto to Dearborn, and I'm concerned about the size of the small articles (21.5 x 15.5 x 9 inch). My current luggage is 23 x 15 x 10, and most "carry-on" luggage that I see advertised is nominally 22 inches with a linear dimension (L+W+D) of 45 inches. Strictly speaking, neither my current luggage nor the normal 22 inch carry-on size would meet VIA specifications for small articles.