I dont know about past(british time)but presently it is not constructed mainly because there are two different political party govt in Punjab and Himachal.
This project is mainly forwarded by MP Hamirpur(H.P) Anurag Thakur at railway ministry but state govt is not supporting for land acquisition issues.
Most of the part is completed in Himachal but Punjab's part is missing(Talwar to mukerian part).
Presently...
more... main focus of govt is on cdg-Pinjore-Baddi railway line because Baddi-Barrotiwala-Nalagarh(BBN) is presently pharma hub of India.