D&H track and infrastructure have been in pretty decent shape over the past decade as there have been CWR installation, tie replacements, rail grinding, signal replacements. I believe that CP made a decision way before EHH arrived to keep freight MAS at 40mph as a compromise between moving time sensitive freight for NS while optimizing $ needed for maintaining infrastructure to a state of good repair. Given the D&H is single tracked with often widely spaced controlled sidings (eg, 25+/- miles) and 8-10 daily movements of often very long freights over a hilly profile, a difference in MAS between 40mph and 50mph wouldn't consistently yield shorter trip times given trains frequently find themselves parked in sidings waiting many minutes for one or two opposing movements.
Here are MAS tables copied from the CP NEUS employee timetable of July 1, 2005 that list MAS for freight for the D&H South:
Freight and Passenger Maximum Speed Table
Unless otherwise restricted:
Freight Mainline:
CPF 467-Interlocking Limits 25mph
CPF 467 to 470.0 30mph
470.0 to CPF 475 40mph
CPF 475 to CPF477 40mph
CPF 477 to CPF 480 40mph
CPF 480 to 486.1 30mph
CPF 480 to CPF 483 CSE 25mph
CPF 481 to CPF 483 CSW 25mph
486.1 to CPF 499 40mph
CPF 499 to CPF 503 35mph
CPF 503-Interlocking Limits 30mph
CPF 503 to 520.2 40mph
520.2 to 520.5 35mph
520.5 to CPF 526 40mph
CPF 526 to CPF 528 40mph
CPF 528 to CPF 554 40mph
CPF 554 to CPF 557 40mph
CPF 557 to 562.7 40mph
562.7 to 563.0 25mph
563.0 to CPF 587 40mph
CPF 587 to CPF 590 40mph
CPF 590 to CPF 611 35mph
CPF 611 to EMT (612.75) 35mph
Sunbury Sub:
Binghamton Container to CPF 648 40mph
CPF 648 to CPF 650 40mph
CPF 650 to 655.3 40mph
655.3 to 656.0 25mph
656.0 to CPF 659 40mph
CPF 659 to CPF 661 40mph
CPF 661 to 663.0 40mph
663.0 to 670.8 35mph
670.8 to CPF 672 20mph
CPF 672 CPF 673 20mph
CPF 673 to Carbon 20mph
Carbon to CPF 679 30mph
CPF 679 (Diverging Route) 10mph
CPF 679 to 681.3 30mph
681.3 to 693.3 25mph
693.3 to 705.3 40mph
705.3 to 706.1 35mph
706.1 to CPF 714 40mph
CPF 714 to CPF 716 40mph
CPF 716 to 716.6 40mph
716.6 to 716.7 35mph
716.7 to 749.0 40mph
749.0 to 749.4 35mph
749.4 to 750.01 35mph
750.01 to 751.0 20mph
751.0 to Sunbury 10mph
Sunbury to CP Kase 10mph
Here is a URL to the timetable (see MAS tables on pages 15 (Freight Mainline Mohawk Yd to Binghamton) and 23 (Sunbury Sub Binghamton Yard to junction with NS at CP-Kase):
https://xa.yimg.com/df/dandh/CP+NEUS+Ti ... e=download