They can bust trades. Go to http://www.iseoptions.com/download/rules.pdf Rule 720 (Obvious errors) I believe 50 cents is the approximate cutoff. However, the ISE has a pending rule that reduces it to 25 cents for options under $3.00 http://www.iseoptions.com/download/SR-ISE-2001-34.pdf
Thanks alot mskl. I perused at the rule book and I think what happened to my trade which I am now confident will not get busted is a block trade > 50 contracts wherein any customer bid higher can get filled at the block trade price, which in this case is 45 cents lower. Sorto like price improvements in the NYSe. It is amazing that right after that big block of calls sales, BMY went down greater than 60 cents. Frontrunning perhaps?