#1That's the key in yours - not that it's a TRSA, but that it's a towered airport at which the ATIS advises pilots to contact CD for departure instructions. It could be a plain vanilla Class D and operate the same way. #2There is no such thing as a "TRSA clearance" for VFR traffic. But of the alphabet airspace classes that have surface areas for airports, only Class B requires a "clearance" for VFR traffic.
#1. I understand having VFR departures calling CD freq at Class C airports but a regular Class D, VFR tower (aka NO RADAR), having VFR departures call up CD is absolutely ludicrous from both a pilot and controller stand point. What are you going to tell them? Ummm, squawk VFR contact ground? Completely pointless. In a radar environment aka Class C or Class D with TRSA, VFR departures are told to contact CD so they can be put on a local VFR or IFR code so they can be radar identified and issued additional restrictions, if needed. If a VFR Class D tower (once again, no radar) is telling VFR departures to contact CD, I would be interested to know what instructions they are receiving. I am a private pilot that has flown into numerous Class D's and this has NEVER once happened to me at a VFR Class D tower... never! The only thing I can think the ATIS would have said was IFR departures contact CD, which should not even be on there because it is implied unless stated otherwise, as others have noticed from time to time "all departures contact ground control freq."
#2. I have discussed this topic ad nauseam with pilots and the truth of the matter is 99% of pilots don't know what the hell kind of service a TRSA provides, even the ones that operate within one. When talking about a "TRSA clearance" we are kind of talking semantics here. You are right in the sense that you do not need a "TRSA clearance" to operate in a TRSA like you would a Class B. That is correct. If you, Pilot X, are flying around smashing bugs in your 152 you can fly within the TRSA without talking to anybody, albeit you stay clear of the Delta, unless you talk to tower. However, since it is a condensed area of traffic, the FAA decided to add the TRSA to essentially provide flight following to VFR aircraft in addition to the normal IFR service that transits the airspace. Due to traffic volume, it is encouraged that you participate, although once again, not required.
However, when you are on the ground at a Class D TRSA, that is a little different story. You will either (A) depart with TRSA services or (B) depart VFR on your own choosing not to participate with the services. All aircraft are assumed to be participating in TRSA services unless instructed otherwise. The pilot must state Negative TRSA service or something similar that does not have any ambiguity. If you do not tell them you are not participating, then what you are receiving on CD frequency is essentially a "TRSA clearance." You will be given a restriction, such as maintain VFR at or below XXX, a departure frequency for flight following, and a local squawk code. You will not directly be told you are cleared to enter the TRSA like you would a Class B clearance but, essentially what you are receiving is a "TRSA clearance." If you choose to not follow those restrictions then you advise the tower and depart VFR on your own without flight following as you would a VFR tower.