maximum allowed platform dwells for the French, Spanish and German HSR services would be useful real world information.

Unfortunately, I don't have those data (if they are fixed at all -- I don't think they are in Germany at least), but I will make some notes.

First, it may be that East Asian high-speed is really a better comparison than Europe. CHSR traffic will be shuttle-like: keeping to dedicated lines with relatively short total travel times. However, In Europe, longer high-speed train runs continuing on conventional track are more typical, especially in Germany. (The exception is Spain, but there, station capacity is adjusted to an expected massive future growth, so currently they aren't pressed.)

So, in Europe, turnaround times may be lengthened by a buffer for delays, and shortened by a service concept foreseeing most of the work (like filling up tanks) during the night, when there is time anyway. As a rule of the thumb, 1-1.5 hours would be normal for stops including cleaning/checking. Some numbers:

• Paris Gare de Lyon:
  
  The surface station has 22 tracks. TGVs depart at a maximum 9 tph, an additional 6 non-TGV trains also depart in the peak hour. I couldn't track down French circulation plans, but extrapolating for a maximum capacity from the minimum 4-minute headways, I get 60-minute turnaround times.

• AVE:
  
  Barcelona Sants, Sevilla Estación de Santa Justa both have 6 normal-gauge tracks for high-speed trains, but only a maximum 3 tph; Málaga's Estación María Zambrano even 5 tracks for a max. 3 tph -- though, not evenly distributed. There are 10 minute headways, so one can assume a capacity of 6 tph with, again, 60 min turnaround times.

• Germany:
  
  The shortest turnaround I found with a brief search was 53 min, for turnarounds including a visit to the maintenance yard: 109 min(!). More relevant for CHSR is the example of the onetime Metropolitan, which ran a short tight schedule between Cologne and Hamburg: turnaround times were down to 34 minutes.

As for East Asia: in Tokyo, both JR Central and JR East operate up to 11 tph, but the former from 4 tracks while the latter from 6. Taipei Main Station has 4 tracks for THSR trains, with a maximum 5tph right now.

Now, it is one thing whether Japanese precision can be copied in SoCal, another is passenger discipline, yet another the size and efficiency of maintenance crews. So I don't think 12tph is possible in the TBT on four platforms (e.g. 20 minute turnarounds).

By the way, is the operation of the 3 access tracks in the tunnel with one track strictly for the total incoming traffic, and two for departures, an explicit design feature, or your interpretation? Because I don't like that. Three tracks with a proper train signalling in bi-diretional operation might be better, but unless Caltrain is electrified and gets modern EMUs, I would prefer to not run 'em on the same track at all.

_{*Lunatic*, n.
One whose delusions are out of fashion.}