Yeah, I don't think Luke's track is in race condition anymore, it was only a dual track though anyway. The only proper 4X track we ever had was at Blacktown, it was the one that Brett Barnes and Dave Flood had built for the 000 games (aka police games). I had the pleasure of racing there (with Brett, damn he's fast, like BMX cruiser World Titles fast, knock em dead Barnsey!) and I can say it was a great track, heaps of fun to ride without being too intimidating for the beginners. Unfortunately it was demolished the week after the race due to liability issues.
I was talking to a bloke from WSMTB club today though, and there are some tracks in the work, pending permission. Hopefully the club will have 3 tracks running in the not too distant future. I'll let you know details if they get the go ahead.