A route that I think you should look at is Canada-London; then Gatwick-Bilbao via EasyJet. Remember, however, that most flights from Canada arrive in London at Heathrow, not Gatwick and connections between the two are tedious, especially when jetlagged.
In Bilbao, there is a city bus from the airport to downtown although I confess that the last time we made this trip that I was defeated by the schedule information posted at the airport and ended up taking a taxi. How's your Euskadi (the language spoken in the Basque provinces)? Better than mine, I trust.
As others have pointed out, there is a good bus service from Bilbao to Irun and Hendaye (and on to Biarritz and Bayonne, by the way, for anyone starting from SJPP). We took this trip in reverse about 18 months ago and thoroughly enjoyed it. It travels through some very picturesque country and you will get a preview of your first few days of walking.
One other thing to keep in mind is that Air Canada (bless their tiny black hearts) are instituting a new route into Madrid. I believe this service starts June 15 (confirm at their website if you are interested) and all flights are through Toronto which is not so helpful if you are starting east of there.
- DR