Once it "comes with the plant", is it in the soil, waiting for the next susceptible plant? After reading a little about this disease yesterday, it seems that ALL boxwoods plus a few other types of plants are susceptible. I can't find information about how it travels from plant to plant or where its hiding in the meantime. Is it possible to go back to the University horticulturist with a list of questions? I think its important to know where the disease comes from (with the plant, in the soil, in the air,...) and how it is transmitted before you proceed with a replacement plan.
I would talk to the grower you got the plants from - if it does come with the plant, there should be some kind of warranty. Usually, plants are guaranteed for a year.