I've noticed recently that the coverage plots (using the online TV Maps feature) contain overpower anomolies for certain stations. Check out, for example:
CHLF-TV Hawkesbury
CHCH-TV-1 Ottawa
CHEK-TV Victoria
among others.
you will see a spike in coverage, generally towards North Northeast. The effective power in that direction is often reported 20-30 dB over the Maximum power.
For example, CHLF's max ERP is 10 KW, but the effective power to the NorthEast is over 2 MW.