I was wondering if you could do a chroot from Freebsd to GNU/Linux, because I know that Freebsd also has a compatibility layer for executable GNU/Linux?
Of course provided that there is support to the filesystem and shell.
If you install linux ABI support on FreeBSD, you can simply execute a Linux binary and it looks like a Linux environment for this application, with the exception that user homes are still available.
You can try it yourself and look at the system by simply executing:
Type for example
uname -a and you'll get Linux version information.
I've also heard about people having Linux running in a FreeBSD jail, but I don't know if this really works well. It may come closer to a chroot environment. And there is also bhyve that does real virtualization.