Complex sentence: In the 1980's some class members were leased to the NSWSRA to operate in NSW, which had also begun the upgrading of some 45 class which at that point were banned from leading.
Split into simpler sentences: In the 1980's some class members were leased to the NSWSRA to operate in NSW. Which had also bought about the upgrading of some members of NSW 45 class which at that point were banned from leading.