SUBL to Hubballi East Cabin(HBQ) is single line, at Hubli East Cabin the lines from Gadag join, from there its double line till UBL station for sure. But it may also be considered 3 lines from UBL East till UBL station as I have seen three signals for those 3 lines, but one is generally used to stable some or the other rake.
So HBQ-JRU should be considered for doubling.