I'm doing some software tests in my company and one question is wether old files can be opened in new programms. According to my google-fu it is possible to open Logic Pro 9 projects in LP 8, but is the opposite possible as well (open LP 8 projects in LP 9) - that's where my google-fu left me?
Yes the session files are fully compatible both ways. Options or plugins from PT9 that are not available in PT8 are automatically disabled (and vice versa).
Track routings are obviously not working if the originally used audio-interface is not available. You'd have to re-route.