There are no doubts that ORD is a very busy airport, sometimes the ATC doesn't use a standard phraseology and the risk of a misunderstanding is very high... but when you're taxiing and you've an obstacle on your way you have to stop even if you have been instructed to move. If an airplane is stuck in the middle of a taxiway and you hit him you are responsible, the ERJ was still occupying the taxiway with its rear part, the crew must be able to assure the correct separation by himself. Awaiting for an official report, according to me there are no excuses!