Almost always larger blocks of stock are traded as crosses because the instit. world is relatively small. All the larger brokers cover the same a/c's & therefore the guy that captures the initial buy or sell order has a huge leg up. On the odd occasion this rule is broken for political reasons because an a/c can only deal with a specific broker but wants the offsetting buy or sell.

IMO there is little to gain from knowing a specific broker is active in ARU. In fact a/c's have been known to spread business around to disguise concentrated activity. The only useful info is total volume, variance of volume to the norm & price change.

Regards

Joltin