It happens all the time. An agent goes from one company to another and brings his clients with him. In the case of baseball agent Josh Yates, he is on to his third company in the span of roughly five years.
Yates began his career as a baseball agent with the company CSMG, which had its baseball division along with its coaches, broadcast, legends and marketing divisions acquired by Octagon in 2008. Yates had left CSMG prior to much of the company being eaten up by Octagon. He had left the company to join the strong baseball division at SFX.
Fast forward a few years and Yates is on the move again. According to an SFX spokesperson, Yates left SFX on January 3, 2012 to join ACES, which is owned by Sam and Seth Levinson. Yates has taken Jon Lester, Mike Adams, and Felix Pie with him in addition to some Minor League players.