>> I do not think this is possible, since only one server can use port 80 to pick up the certificate.
You underestimate how cunning NetTalk is!
However I'll preface by saying that I've no idea if they will actually co-exist - it'll depend on how cunning the TS Plus server is.
In the NetTalk setup there's a setting there "Acme Web Folder". Typically this is your web folder, and you listen on port 80.
But it _could_ be any folder on the drive, and so you could point to the "TS PLus server web folder". The challenge file is create there, LE connects to Port 80 to get the file and (hopefully) the TS Plus server serves it.
In other words it doesn't matter who is listening on port 80 (it doesn't have you be _your_ server) as long as the file is supplied to LE when it is requested.
This approach is used a lot when there are multiple NT Web servers on the same machine, or a mix of servers like IIS, Apache or NgineX.
It's technically possible for TS Plus to suppress serving this file, but hopefully that's not the case...