Compositing renderings with glass

I’ve got a not-exactly-Rhino question here. If I’m working on a shot of a car interior like I posted here, rendered in iRay, Switchblade Flying Car , and I want the downstream graphics people to be able to swap out the background easily if they want. I send them a TIFF with an alpha channel, fine, but if I load that alpha channel in photoshop to knock out the background, I can still see the backplate due to…is it looks like reflections, the glass not being perfectly transparent? So I’m wondering what the workflow is that “real pros” use for this situation, I guess ideally being able to swap out the background while keeping the reflections and translucency.

If possible render the reflection pass to a separate channel, along with an object ID or material ID pass. Use the latter to mask out the former.