In regards to "Can another game that isnt based off the source engine have its stats collected?"
No is the short answer.
Nooooooooooooooooooo is the long one
Valve themselvs have built the stats sending part of the components required for this directly into their source engine (log_addaddress and log on are the commands), because of this and how the stats are sent it is near impossible to get stats out of another game that does not use the source engine and include them in the stats.
While I would love to enable this functionality, i do not feel that the time to reverse engineer some game to inject some custom made DLL or use memory reading to collect stats then send it in the same format as the source dedicated server does is a good way to spend our time, it's also really difficuilt!
Since i have been home I have found that there is a problem with HLStatsX:CE when the SteamID's changed their format...
While this did not exactly ruin the stats for us, it did however mean that if you changed your user handle during the event your stats will stop being collected for user A, and start being collected from fresh for user B - i believe i have found a fix for this and will see how it works for next time perhaps...
I do however agree totally with "Please organise more games where I can win shit", yeah deffo and this is a fault by us/me/etc - more organised games will make an appearance at the next LAN.