Hi,
FOP2 just launches the Monitor command in asterisk. Up to that point, it is up to Asterisk and its dialplan. The monitor command in Asterisk stops when the original channel is terminated, when you transfer a call, the original channel is terminated. So, you have to modify the asterisk dialplan to see if monitor was enabled and start monitoring on the 2nd channel. Fop2 does not handle the dialplan, it fires the monitor command and "forgets".
There are a number of complications trying to "follow" this kind of information, that now that I think about it, it might be possible to at least set a channel variable in fop2 with the hopes you can read that variable to restart the monitor command if a new channel inherits that. I think that the latests FreePBX releases (2.10 and up), includes an updated dialplan that does this (it can continue a recording after a transfer), but I am not totally sure about it.
I think Elastix is using FreePBX 2.8 or perhaps 2.9, but not the latest 2.10, so you won't be able to test it outside of fop2 to confirm.
The point is that FOP2 tries not to be an "intruder" in your dialplan, its actions are pasive unless you perform a special action with the action toolbar (like hanging up, or redirecting transfer a call, etc). But after that action is performed, the dialplan should kick in, for example you can terminate a ringing call from fop2, some people might want that hanged channel to be terminated, while others might want to let a caller be connected to voicemail. Those things are handled via dialplan and asterisk settings, not by FOP2.
Reinitiating a recording after a channel is terminated might be considered (or not) intrusive, as it will affect a possible dialplan logic without user/admin knowledge. I will make some experiments and see if I can set a variable and if that survives transfers and can be used to restore recordings, then I will decide if its intrusive or not.
Best regards,