Yes, P4 can ascend , but please see attached pic
An average weight of an ICF coach would be around 45 Tonnes including payload. with 24 coaches, you are looking at 1080 tonnes,
which means a train like GT or TN can easily take a 1:100 gradient at 60kmph, but as it becomes steeper, the load carrying capacity decreases geometrically. There will be not much diff between 1:200 and 1:100, but once you going down to 1:60 or 1:70 a P4 may be able to haul 16 - 18 coaches and that too...
more... at the limit. I guess P4 can handle the load in the mentioned sectors with around 16 coaches, provided it is CBC coupled.
45 tonnes is arrived at based on following
AC coaches is approx 60 Tonnes
Sleepers approximately 35-40 tonnes