The Adelaide crew are not casuals, they are fulltime. Casuals have also not been hired in Perth since something like 2009, and that was a once off I have been told they will never do again.
Adelaide crew fly to Ballera once a week (or they did when I was crewing with them in late 2010) and the other days are Moomba twice a day. Typically you'd do a Moomba return and that'd be your duty done for the day, but often you do both the Moomba trips. It can sometimes feel like a long day (I can't remember how long it was exactly...maybe about 10 hours?). That being said, the service is extremely regimented and it all flows very well, and isn't hard. It is very different to how the operation runs in Perth, but this is to be expected when the base in Perth is so much larger than Adelaide. The training team over there are also a terrific bunch of people.
The Perth base scarcely ever does 'special charters' anymore - they do not have the time, aircraft or crew for that. In 18 months there I did one special charter, and that charter in itself was a once in a lifetime kind of charter. And I only was chosen to do it because I was part of the check and training team. 90% of your roster in Perth will be Barrow Island flights - this is the largest contract and the one they devote practically all their energy and money to. This contract is great in requiring many new lovely RJs and they seem to be getting them all the time!
Sorry I don't know where you could find copies of the aggreement online.