When you purchase 016 ticket stock, you may tend to be buying fares that earn 100% mileage, but the two are completely coincidental. For example, K fare on Air Canada between Toronto and Vancouver - earns 25% PQM on MileagePlus. But - that would be solely an Air Canada ticket, and United isn't allowed to even sell it.
The minute you have 016 ticket stock, that's an Air Canada flight coming into the USA, and therefore, even if it WERE ticketed with Air Canada, it would earn 100% PQM on MileagePlus.
If you even COULD buy an ultra cheapy low fare with 016 ticket stock on, for example, Egyptair - it would earn less than 100% mileage. The company that sells the ticket has nothing to do with earning rates for PQM.