Last time I dealt with this, customer service said it would be non-earning since it was paid for entirely with WestJet Dollars.
That being said, I'm interested in the following assumption. If I paid at least $1 of the base fare with cash, it would become eligible to earn WestJet Dollars (I'd earn on the $1 I paid). Would I then be eligible to earn Delta SkyMiles on the entire ticket since it's now eligible for earning?