Doesn't seem to be shown on the photos I've seen of ON 17 and ON 417 just now. I'm pretty sure I didn't see any when I was in Ottawa in 2009 which is why I wanted to check.
Do Ontario and Quebec even post TCH shields?
The majority of Ontario's population is probably south of the TCH anyways.
Yes the shield is posted along with the provincial route number in both Ont and Quebec.
The 401 corridor is south of the TCH and the closest the TCH gets to Toronto is about 80kms.
In Ontario the TCH splits at Ottawa, and follows ON-417/17 west to North Bay and on to Manitoba, and ON-7 west of Lindsay at JCT ON-12 north to Orillia to JCT ON-400, to meet up with ON-17 at Sudbury. This is know and signed as the Central Ontario Route. AT this JCT of 7 and 12, is the closest west in Central Ontario that the TCH gets to Toronto. At North Bay, the TCH splits again to follow ON-11 (Northern Ontario Route), and ON-17 then meets up at Nipigon (Lake Superior Route). The thinking at the time was to provide as much coverage of Ontario as possible. Also interestingly enough Ontario does not have a HWY 1 as the government at the time (1920's) didn't want towns and cities fighting over the possible routing of a road.