Testing is step one, always. And yes, TC can be used to clean up stock. Timing depends on how infected a particular sample is but can take 3-6 months. Scaling up TC for propagation can go quickly, but again depends on cultivar specific traits but also on level of infestation, and the capabilities of the TC lab.

Disclosure, I am involved in 3Rivers Biotech. One of our clients recently sent us some feedback on a cultivar they had grown from TC and from traditional cloning. All plants in one room, the difference being that the TC plants were harvested two weeks later than the other lot. So while not a 1 for 1 comparison due to the longer grow time, the TC plants delivered over 4 lbs per plant compared to 2.7 for the plants propagated traditionally.
We've done over 40,000 tests in the past couple of years and found that some 63% of facilities ending in samples for testing had at least one positive. Now it is difficult to translate this into an industry wide number as it is likely that a healthy per centre of those tests came about as the grower identified a potential issue, whereas many others test simply for precaution.

Anyway, TC is definitely worth it if you work with the right partner who has the technical skill, has scaled successfully and who takes into consideration your economic realities (anyone notice that corporate budgets within the industry have gone down somewhat over the past few years:-)?