You can, however, bid from ERJ to CRJ same seat, just not the reverse. According to the latest MEC email, if you displace into "higher" equipment, you cannot vacancy bid back to the "lower" equipment once this settles down. I think this has already been stated, but just wanted to try to clarify. A San Juan ATR CA, if displaced to Dallas EMJ CA, cannot vacancy bid back to Dallas ATR CA even if his seniority will hold it.