Thanks for tagging me. To the best of my knowledge, the information in the RTI reply is not correct.
The Vijayanagar express was introduced between Guntakal and Hubli from January 26th, 1976. I have the SCR timetable of 1978, and the Vijayanagar express was operating between Guntakal and Hubli as of June 1978. Sometime around 1983, the Vijayanagar express was extended to Vasco-da-gama
But there was a Bangalore-Hubli passenger via Guntakal that ran in the MG days. This passenger itself was earlier running...
more... as Mysore-Hubli passenger (it was a mail train the SBC-MYS portion and a passenger in the remaining section) via Guntakal.
In 1983, after the gauge conversion of the SBC-DMM line and the construction of the DMM-GY broad gauge line, a day-time passenger numbered 91/92 was introduced between Bangalore and Guntakal. Later this was extended to Hospet, became an overnight train and was upgraded to an express. This express was renamed as 'Hampi' express sometime in the late 80's. After the GC of the Guntakal-Hubli route, it was extended to Hubli.