I used JTossim until 1.5 maybe 2 years ago, but from the version I used I remember that Lorenzo Keller, who developed it sent me some sample network topology files. However, the tool could also take as input the TOSSIM topology files (it is fully compatible with it), such as the one attached for example. But they are not .pos as you mentioned, rather .tmp.. I will look in my archive and try to find if I have something. If I do, I'll let you know..
sorry its been a long time but I was a bit busy developing some software for deterministic Ethernet.. I searched on my mailbox and on my previous work and did not find any .pos file as you mentioned. However Lorenzo's mail address is: [email protected] you can contact him he's always helpful and accurate in his answers..
I'm sorry I can't help, but at that point I was studying the energy consumption and modeling of this type of networks and was not focused too much in the topology..