There are currently 5 channels from Toronto, see [Link: remotecentral.com]
for list and transmission power. All are low power, some VERY low power and directional. I cant speak for reception possibilities in Niagara Falls, hopefully someone else closer to you can comment ?
CBLT-DT (5.1) uhf20
CBLTF-DT (25.1) uhf24
CFTO-DT (9.1) uhf40
CKXT-DT (66.1) uhf66 (Theres a repeater in hamilton also - see list)
CITY-DT (57.1) uhf53
There are another 3 channels coming soon, hopefully, but they'll also be low powered.