It'll definitely be cheaper for IR to construct, but I've lived in the hilly areas in Rajsamand and Ajmer districts. Yahaan jitna kam development hai, woh dekh kar lagta hai ki the cheap, fast transport that railway offers can be life-changing for the people here.
To give an example of how slow things go in this part of the world: the Delhi-Mumbai highway formerly known as National Highway 8 runs through this area. Till 2012, the part of the highway that runs from Udaipur to Beawar was an undivided two-lane...
more... road with very varying topography, poor maintenance conditions, and a few very steep passes (mostly around Udaipur).
One good-ish sign is that the MVJ-DOHM GC project is being funded using Gati Shakti. This means there's a good chance they'll connect it to the AII-MJ mainline.