I have 3 thoughts:
"each limiter's output will feed multiple bus segments" my not be convenient for operations. A short in one segment will stop trains in all other segments which will be frustrating to your train crews.. I suggest having each 'circuit breaker' power a contiguous section so a track short creates minimal train operation disruption.
"each of those runs will exceed 30' " -- Can you relocate your boosters to avoid exceeding 30' main bus runs? A 60' length can be powered as 2 30' sections by lacating the booster with a main bus configured as a 'T." You could power a 60' section on both levels (120' total) with a single booster without exceeding 30' main bus length. This will mimiize (and possibly eliminate) any need for 'snubbers.'
Circuit breaker selection - consider using 'single' breakers rather than a 'quad' breaker. Individual breakers can be located along the main bus creating a 'sub-bus' feeding each section. This mimimizes the amount of large gauge bus wire needed (and mimizes the 'spaghetti bowl' of wiring under the railroad). I prefer the PSX breakers; others may offer other suggestions. (Note - a PSX4 is actually 4 indiviual PSX breakers that can be snapped apart for individual installation.)
Designing to 'best wiring practices' now will be benficial in the long run. You may have to think 'outside the box' for the best solution for your railroad.