Does Paris runs or just the CBTC capable of running? You need more than CBTC to run at 85 second headway. Loading/unloading time became huge problem at that interval.
I just checked Line 14 schedule and the most I can find is 34 train per hour, which is approx 105 second headway.
I am not saying that CBTC isn't capable of running higher interval than regular ATS and wayside signal (which is actually a very old technology), but in most case it doesn't matter. Even without moving block of CBTC, a very short static block (say, 100m) and in-cap signally should theoretically have the came capacity as CBTC.
For local trains you need your loading and unloading time to be as fast as possible anyway. People have places to be, waiting around on your trains and platforms is not on the list of things they want to do. It is even worse when they are waiting around not moving at stations they don't want to get off at. 60 seconds is the absolute longest any train door should be open for, and 45 is reasonable. (it can be pushed to 30 or even 15, but that starts to be impossible for the disabled and so not worth it)
London runs 36 TPH on the Victoria Line: https://www.londonreconnections.com/2017/ninety-second-railw...