no - PMG does not have support for SRS - from a quick look online there are a few projects that implement this for postfix - some seem even packaged in Debian: https://github.com/roehling/postsrsd - It might be possible to adapt the postfix configuration of PMG to use that - but it's nothing we support officially (and it's nothing we've tested).
Well, since PMG would be in front of several mail servers, since each mail server needs additional components and config to perform SRS, I thought I'd try to do it all in one place and only once.