Just a quick observation following the recent stress tests of Multiplayer Surveyor this week.
Each time we managed to successfully crash the server's game instance - mostly via high-speed collisions/ derailments on purpose - (crash to desktop in my case several times) a lot of orphaned, 'new' assets appeared in my Open For Edit folder.
(You can safely delete these, as you cannot use them to 'recover' the edits when the remote server session is restored).
So, check for any 'Open for Edit' items in your local Trainz 'editing' folder following any such crash.
Biggest issue for MPS in my opinion is rogue participants sabotaging the route by creating spurious terrain features and destroying existing ones - something that can be controlled by the MPS route owners in the future.
The number of concurrent users doesn't seem to be much of an issue or concern even with the relatively modest server configuration used for these stress tests. The numbers can be easily scaled by boosting server capacity, load balancing and bandwidth, it would seem.
I was very impressed by the reasonably low latency and high responsiveness of the system whilst in route-edit mode, even from NZ, which is many hops away from the USA-based server.
Indeed, I was able to retain all my ultra-quality visual appearance, draw distance, and Trainz performance settings as I use for my local desktop experience here during these MPS sessions. Almost indistinguishable in terms of speed, lag, responsiveness and smoothness from the local desktop experience. Impressive! A tad more scenery item (random rocks, etc.) 'pop-ups' occasionally, as you zoom around the landscape, which is explicable perhaps more in terms with the dictated visual distance settings applied server-side.