If it's happening, then it's good news. I can't connect my Idea sim (Home circle) to Vodafone 4G when I select network manually. Another sim which is roaming (Karnataka Circle) is able to connect to Vodafone 4G and has better download speed than Idea network. Anyone can try and test. I don't think they really merged their towers as you can see from the government website tarangsanchar.gov.in the networks attached to a tower can be seen for any location and on a single tower the networks present are listed in which Vodafone and Idea are seperate.