There are different types of crossings. If you buy from someone who happens to be selling via the same broker it can show up as a crossed trade. There are also actively brokered crossings that are flagged on screen before being crossed. And there are special crossings which are done off market.
Here is a link on the asx site that describes the different crossing scenario's.
Hmm, but wouldn't a lot of trades be crossed then, such as comsec to comsec broker trades? Could we further reduce brokerage costs if we had a 'private market' showing those shares that are on Bid/Offer by a particular broker?
heh - guess similar to same provider mobile calls!