It seems reasonably likely they would have also been cut if Clinton had been president, due to the review requirement that was built into the regulations themselves.
The 2015 law that required ECP brakes also required before they went into effect the government ask the National Academy of Sciences (NAS) to review the safety assumptions that the regulations had been based on and report whether or not those assumptions were correct, and revise or rescind the regulations accordingly.
NAS completed that report in early 2017 and it said that it was unable to conclude that ECP brakes were safer. There simply had not been enough actual tests to generate the data needed to reach a conclusion.
Given that NAS report it is hard to see how any administration could have justified not rescinding the regulation.
Unlikely they would have been cut under Clinton. And I don't think the required review you are talking about is concerned with safety. It's money. The review that is required is actually a financial review that decides if the cost of the safety regs in question exceed the cost of potential accidents. This analysis had already been done. However, the Trump admin had the calculation done again, I would assume after putting their own people in place and they found that the regulation was too costly. Big errors were made in their calculation but they claimed that even after fixing the errors, it was too costly. So they rolled back the regs.
That being said, the regs in question only applied to certain hazard levels and the train that crashed did not meet that level because it didn't have enough cars with hazardous materials.
I'm talking about the report that was required under Section 7311(b) of the FAST Act, Public Law 114-94 [1]:
(b) Emergency Braking Application Testing.--
(1) In general.--The Secretary shall enter into an agreement
with the National Academy of Sciences to--
(A) complete testing of ECP brake systems during
emergency braking application, including more than 1
scenario involving the uncoupling of a train with 70 or
more DOT-117 specification or DOT-117R specification
tank cars; and
(B) transmit, not later than 18 months after the
date of enactment of this Act, to the Committee on
Transportation and Infrastructure of the House of
Representatives and the Committee on Commerce, Science,
and Transportation of the Senate a report on the results
of the testing.
and the review required under 7311(c):
(c) Evidence-Based Approach.--
(1) Analysis.--The Secretary shall--
(A) not later than 90 days after the report date,
fully incorporate the results of the evaluation under
subsection (a) and the testing under subsection (b) and
update the regulatory impact analysis of the final rule
described in subsection (b)(2)(A) of the costs,
benefits, and effects of the applicable ECP brake system
requirements;
(B) as soon as practicable after completion of the
updated analysis under subparagraph (A), solicit public
comment in the Federal Register on the analysis for a
period of not more than 30 days; and
(C) not later than 60 days after the end of the
public comment period under subparagraph (B), post the
final updated regulatory impact analysis on the
Department of Transportation's Internet Web site.
(2) Determination.--Not later than 2 years after the date of
enactment of this Act, the Secretary shall--
(A) determine, based on whether the final regulatory
impact analysis described in paragraph (1)(C)
demonstrates that the benefits, including safety
benefits, of the applicable ECP brake system
requirements exceed the costs of such requirements,
whether the applicable ECP brake system requirements are
justified;
(B) if the applicable ECP brake system requirements
are justified, publish in the Federal Register the
determination and reasons for such determination; and
(C) if the Secretary does not publish the
determination under subparagraph (B), repeal the
applicable ECP brake system requirements.
The 2015 law that required ECP brakes also required before they went into effect the government ask the National Academy of Sciences (NAS) to review the safety assumptions that the regulations had been based on and report whether or not those assumptions were correct, and revise or rescind the regulations accordingly.
NAS completed that report in early 2017 and it said that it was unable to conclude that ECP brakes were safer. There simply had not been enough actual tests to generate the data needed to reach a conclusion.
Given that NAS report it is hard to see how any administration could have justified not rescinding the regulation.