Back in the day, you could do. I was tutored in one of the Quakes (Q3a I think? Might have been Q2) by a friend who was on a Dreamcast while I was on a PC. There was a specific official patch level I needed to be on, but it worked fine.

He was a Q2 national champion or something, it was really helpful, although whenever we stopped for a break and have some combat, he'd pwn me like a n00b.

http://www.swyx.com/ is a fantastic product, the graphical scripting editor is amazing, get a good reseller and you'll have top notch support and you might well find the TCO is lower than for alternative systems like Asterix. If you give Swyx a call, they can probably recommend you a good reseller. (Full disclosure: I work for a UK-based Swyx reseller)