Mostly justified, considering the fact that have many sponsors and clients, they can pull this trope a lot, even in most non-union dubs when it come to re-using the same talent pool of actors they are familiar with.
The Other Darrin: Usually averted as for the most part sequels and spin-offs to shows they have already done are generally good about maintaining the original voice actors. Dubs for the sequels to Rozen Maiden, and K-On!! were able to secure all of the original voice actors despite being recorded some time after the original dub. Even the dubs for The Disappearance of Yuki Nagato-chan, and Persona 4: The Animation brought back most of the original voice actors but with a few recasts for voice actors who were unable to return. However despite dubbing the original adaptation of Fate/stay night when Fate/Zero received a dub many of the returning characters had newer voice actors and this same cast along with new recasts would happen again with the dub for the Unlimited Blade Works anime.
Production Posse: Bang Zoom! has traditionally use the same voice actors in many of their dubs, especially when using newer voice talent (usually from the ones from their yearly open auditions to several anime or video game projects from Anime Expo) since 2011. However, they still use some veteran voice actors (particularly the ones that have worked at the studio for a while) on an occasional basis.