Heading eastbound out of NWK Broad: track limit is 30 over the drawbridge and the first "rightward" curve; after that, limit goes to 55 from Harrison Interlocking to the "leftward" curve and then 75 on the straightaway; HOWEVER, if you are a midtown direct service, you are under a 45 mph signal restriction for the switches at Kearny Interlocking that'll take the train onto the NEC.
So really on M&E east of Summit, the only stretches where an MTD could get a decent 75mph+ run is just west of Maplewood to west of NWK Broad (approx where MBN comes in) - a 6-7 mile run & NY Penn to the Kearny interlocking (I'd imagine about 5-6 miles?). That is roughly borne out by my experience on the 6437 Gladstone Express out of NY Penn which has Maplewood as the first stop.
1) 2-3 min to get through the yard and to the tunnel @ NYP
2) 15 min to NWK Broad (sprint to Kearny interlocking/dead zone & crawl to NWK)
3) 7-8 min to Maplewood - so about 24-26 min absolute best case for the 18 mile run. Average is closer to 28 min
Maplewood to Summit is again slow (45-50 mph?) mainly because of curves I imagine.
And, to earlier points about "high platforms" saving time, this particular train has a large number of Maplewood bound commuters - and takes almost 3 minutes to unload. I'd imagine, having a high platform at Maplewood could cut that in half or less