A PT is not for the benefit of ATC... they would have cleared the flight for the approach only after the previous lander was reported down by the tower.
I'm only going to do a PT if there's no IF, no lead radial, or if I'm inbound from a direction where the PT makes sense.
If they were holding everyone at the VOR, then yes, a PT via QB is about the only way to conduct the approach correctly.
I miss the good old days in YTS of using all the navigation tools- ARC's, PT, circling- all to move traffic as expeditiously
as possible in a non-radar environment. Required everyone to be in the loop and on their game. But I'm weird like that
As for not being able to go to any fix direct, I'm not sure why not, but I'd assume it was for separation from the previous traffic? But altitudes would be the trick here I'd imagine (like in YTS)? I don't know- I'm not a controller... but can't see why you can't do the RNAV to any runway either (unless it specifically says RADAR REQ'D). Perhaps an airspace structure thing?
In the case you mention, the problem becomes one of "airspace to be protected". On a NAVAID airway, the width of the airspace to protect is about 8 miles (4 either side). On RNAV routes or point to point navigation, we have to protect 10 miles either side of the track. You can see how this quickly becomes problematic. To take someone from PESAC to ALNIB or KAVAT, the swath of airspace encroaches on other sectors and departure routes. Furthermore, we don't actually have a plot board where we can draw this out. so if someone else is in the airspace, we then have no way to determine for sure if their airspace blocks touch or not. We're therefore stuck with not many options to improvise and we chose to use something very simple (if grossly inefficient). The tracks to the VOR are routes that are 8nm wide. That helps us clear up some departure routes should they be needed. They all lead to a hold at the YQB VOR, which has it's own defined airspace block. From there, we know at what distance we can climb or descend other traffic.
This is something that happens very infrequently and for which we don't train very much. Our goal with these non-radar procedures is to offer some service with as little complexity as possible for the controllers involved so as to avoid jeopardizing safety. If procedures are too complex, we risk having confusion as to what rule can be applied where. Don't forget, our people in CYQB TCU are trained with radar which they use 99.99% of the time. We realize that at that moment when our radar goes off, there are many other airports up north that can handle more traffic than us. We know it and it's frustrating for us too! But we can't make complex procedure that people might never use for months or years. That would be unsafe. The controllers that specialize in "procedural" control and work those airports up north with stream lined procedures do so with great efficiency because of the procedures they know, train and work with.
Hope that helps clarify this! If you have more questions, don't hesitate!
QB & OW TCU