A quick search for
YYZ-LIS TP (stop)
LIS-LHR TP (<24hr to avoid UK passenger charge)
LHR-YYZ AC
TP is YQ-free, yields $401.06 for 1 passenger (all $270 being carrier surcharge coming from AC)

I know there are YQ regulations in certain countries, but I don't see any such in that itinerary, so ~$260 is incredible - and almost certainly a mistake, I have been seeing more and more trips with strange YQ lately and wasn't able to get the same fees via the phone/website. I definitely wish it was reproducible as the availability of LHR-YYZ is plenty vs lack of ZRH-YUL-YTZ award space.

Taxes Breakdown
Canada Domestic/International Airport Improvement Fee $25.00
Canada Harmonized Sales Tax $3.25
Canada Domestic/International Air Travel Security Charge $25.91
U.K. Domestic/International Passenger Service Charge $39.90
Carrier Surcharge $270.00
Portugal Passenger Service Charge $29.50
Portugal Security Tax $7.50
Total per passenger $401.06