Secondly, even when you have managed to get a spread order into the market, I am curious as to how it is going to be filled. The way I see it, there are two options
1) Look for an existing spread order that is already out in the market and try to fulfil it that way, eg if you are trying to buy a butterfly, the broker will try to find somebody that is trying to sell the exact same butterfly and then marry them together. In a small market such as Australia, what are the odds that a butterfly with the same strikes, expiry etc etc matches what you are looking for.
2) The broker dissects your butterfly into the different legs and then tally up the various INDIVIDUAL debits and credits to see if it meets your credit/debit requirements. This way, if you were trying to buy a butterfly, the four individual legs could come from four different traders.
It would seem to me that option 2) is more likely, as option spreads would probably cease to exist (at least in Australia) if option 1 was reality. However, I suspect that the methodology adopted by different brokers can vary.
I would appreciate any feedback, as I have not used any spreads because of the lack of a suitable broker. I know that etrade will eventually introduce multi-legged option spreads online, but how long will it be ??