You will not know your equipment until the first day of class. They will tell you what they need and you will pick what you want.
....here's the catch. It is in seniority order from the oldest to the youngest. They could only have E190 JFK one class and only A320 JFK the next class or any combination of equipment and bases. Your equipment will depend entirely on what the company needs at that time as well as what your seniority can hold.
Most companies operate this way or close to it.