I do not work with Mason bees, however I work with the parasites, from the parasitic wasps, to mites that can overwhelm colonies. A colleague has Mason bees as a hobby and he uses a knotwood (instead of the cardboard tubes) and frankly does not notice issues with his colony of any parasitic wasps, though the mites are a problem for the larvae.
In learning about the bee and their parasites; the "bible' of the Mason bee specifically is a book by Brian Griffin, The Orchard Mason Bee'. I have his 1st edition, I have heard the 2nd is better, if that's possible but really don't have a need for it.
I've noticed in previous threads that this seems to be a very viable opportunity for you. I wish you luck and your continued exploration of the bee world and specifically the underappreciated Mason bee. Here is a link to an hobbyist that my friend directed me to a few months back just for fun. And if I wanted a hobby this would be it, but climate in my area is not really the best suited for this unsung heroes.
http://www.tallcloverfarm.com/224/baked-beans-bamboo-beesrecipe-for-a-mason-orchard-bee-home