I think you'll find that the large BK based "commercial" schools train their pilots to make the following calls..
1. Northbound at PRT, identifying current position, altitude, altitude on climb to, direction AND a request for QNH. ie "Syd and all stations ABC a arrow is parramatta, 1500 on climb to 2000 northbound request QNH"
2. Southbound at BBG, once again with current position, altitude and direction. ie "All stations BK lane, ABC is BBG at 2500 southbound"
Also southbound/westbound Navs when overheard YHOX or between YHOX and YSCN or YHOX and YKAT
3. Position, destination, altitude, altitude on climb to and QNH. ie "Syd and all stations ABC is overhead YHOX at 1500 on climb to 6500, tracking Camden thense Canberra, request QNH".
I can tell you that in the many times I've travelled along the lane and also South and West that these calls have greatly helped with seperation. Calls have also been useful when travelling from YKAT-PSP along the unmarked lane between the highways and the restricted area (this is especially so when this area is quite busy late in the afternoon).
The calls provide:
1. Situational awareness - you immediatly know where your traffic is, you are not just relying on "see and avoid" during what can be time crictical phases of the flight or in times where the weather may be marginal VFR
2. QNH - We all know how to read a forecast but how often is the QNH different, sometimes to an extent that it could have you clibbing CTA if you weren't using the updated one.
3. A record of you. This was drilled into me. By making this call you are on tape, the time you are at this particular position is there, as are your intentions. If you do happen to go missing this assists authorities.
We have all had calls held up by people making unnecessary calls yes, but it seems education is the key, removing the calls altogether takes away the important situational awareness they provide.
Theres my 2 cents!