Lets not forget ACSES was put into place because of accidents in Boston and Maryland along with the introduction of the Acela's. So it wasn't always CA. Also keep in mind cab signals were in effect when Chase and Boston Back Bay incidents happend.
The cab signals on the Conrail freight train that overran the stop signal were not equipped with speed control, the alertor whistle had been disabled and the crew was high. Also, which accidents are you referring to which ostensibly lead to ACSES? Although hardly pushing the bounds of railway signaling technology, ACSES is basically a pilot programme that has only been installed on the least complicated parts of the NEC. The fact that it was no adopted more widely in the decade since probably speaks to its costs and benefits.
I can see both sides of this argument. MNRR already has a superior safety record related to its signal system. As I understand it, ACSES is an overlay on top of ATC. Does it make sense to add it to the NH line? Probably, since that would give Amtrak a single system Boston - NYP (and the M8's will have it). Of course, then maybe the feds/Amtrak should pay for it. It may even marginally improve Amtrak's speeds on that stretch (marginally being the key word here).
It's not going to improve the speeds much as right now the speeds are A) determined by the line geometry and B) deterlined by MNRR's willingness to maintain the track to various standards. At 75mph MNRR can keep most of the NH Line at Class 4 instead of the more expensive Class 5 or 6. If there were real benefits to PTC I would be all over it, but in all likleyhood it will not raise speeds and it will not increase capacity.
I don't know what sort of games the MTA is playing with its ACSES cost estimates. They do seem a bit high for me for what should be, in theory, a simple overlay system, but if they are really looking at dropping something like 700 mil that's just not worth it.
I had one more example for the ever so safety consious Dutch. Every year more than a few people fall or jump off of station platforms and into the paths of MTA trains. As the number of fatailites caused by this greatly exceeds the numbers killed in train accidents clearly the MTA should prioritize the installation of automated full length platform "screen doors" to increase safety. I also assume that you drive a Volvo because despite its premium price its marginally better safety in highway accidents is worth it. Hey, why don't we just limit all trains to restricted speed and put a second engineer in the cab. that will REALLY make things safe!!
I'm not trying to be a dick, just showing that there is no such thing as 100% safety. We must somehow make choices about how much we are willing to sacrifice in the name of safety/security. Blindly telling people to "please think of the children" is neither rational nor productive.