A C550 maneuvered to avoid VFR traffic entering the pattern in conflict with their IFR departure procedure. The reporter feels a non-standard procedure for receiving their airways clearance and departure void time may have contributed to the event.

Narrative

After engine start; we taxied to Runway 17 for departure. Other aircraft were holding for departure. When we called ATC for our clearance; we were instructed to call an 800 number for our clearance. Very similar to operations at an uncontrolled field. After making phone contact; we were given a clearance and a four minute void time. We were surprised that a void time was issued as we had contact with SOCAL via VHF radio. Our clearance was to comply with the TRM Departure Procedure and expect radar vectors for PSP..PMD..SNS; climb and maintain 8000 feet. The Departure Procedure off Runway 17 was a left turn to track out on the 109 radial. On departure; (still on TRM UNICOM) we encountered a VFR aircraft entering on the left 45 for Runway 17. Due to the traffic and VFR conditions we made a slight deviation to the north for separation. This traffic was displayed on our Type 2 TCAS as a TA. We were unable to advise ATC of this due to radio saturation and the deviation was; in our opinion; very minimal and in VFR conditions. When contact was made with SOCAL ATC; they said a possible pilot deviation had occurred. We intercepted the 109 radial and very shortly afterward were given direct PSP. The problem was that we had been given the clearance via phone; but expected release time from SOCAL via VHF. In the process we were rushed to meet our void time. This is a nonstandard procedure. We should have been given our release time via VHF. If SOCAL wants to use this procedure during periods of high workload; then this procedure should be noted to operators via AFD; NOTAMs; or other form of textual description. I eventually spoke with SOCAL via telephone. They agreed that the release time should have been given via VHF. Although they said no pilot deviation would be filed; I feel that by explaining our situation it would help others flying out of the TRM Area.