You are hearing the Skywatch Traffic Airplane.
They transmit on 455.9625 and the base talks back to them on 450.9625
For the 2 way traffic you can put in the UHF trunked system or just listen on 461.5625 (or the in put 466.5625) but if you do not program this as a trunked system with the talkgroup you will hear other uses on the system including Johnny Rooter Plumbing. Monitor during morning and evening rush hour. There are certain laws that apply to monitoring these types of transmissions so monitor responsibly.