I personally haven't seen BSNL branding on towers but since most of the infrastructure is shared we no longer see the branding on antennas like we used to for Rcom and Etisalat.
As for the network scan in Mumbai I am able to see 6 4G networks including Jio, Airtel, Vi, Rcom, Aircel and Dishnet. This is kind of peculiar, suggestive of Aircel or Dishnet MNC having been allotted to BSNL for Mumbai circle. But I have at times seen CellOne network in scans as well.
No idea as to when the Mumbai or Pan India 4G launch of BSNL will happen.