So if four are required for 100% coverage of revenue runs, and two have been released and will be placed into service towards the end of May, and my northbound run is May 25 (with the train that continues on and arrives in SEA the evening of May 26) and my southbound run is May 27 (with the train that left SEA on the morning of May 26--in other words, my northbound and southbound trains will be different consists), then there's a 50% chance that one of my trains will have the PPC (assuming they are running the two they have now by then)?
With those odds, I think I'll go ahead and keep my reservation with the roomettes booked both northbound and southbound!
Well, IF it is so that there will be two PPCs operating, your odds are better than 50% that one of the trains will have a PPC. In fact, I think they're at least 2/3. You've got a 50% chance that the train you take northbound will have it, and if it does you also have a 33% chance that the southbound train will as well (you'll have been on one with, and one more of the other three trains will have it, too). If your northbound train doesn't have it, then you've got a 67% chance that the southbound one will!
If the PPCs are deadheading to Los Angeles, maybe that will mean that they'll head out two in a row with them, then two in a row without. That will mean that you're stuck back at 50% (but in that case if you get one with it NB, you'll also get it SB).