Two sets of photos, one is a newish design of installation known as MPBS - Mobile Phone Base Station and is designed to allow mobile phone masts to be installed on existing HV transmission towers taking its supply from MV supply via a transformer
The other two are just examples of MV transmission, but vertically aligned, due to the other set being removed.
I've noticed that sort of base station on HV pylons and two thoughts come to mind. 1 Does the HV transmission system have to be shut down for them to be worked on? and 2 Are there special measures incorporated to overcome EM interferance? The field strength must be enormous where they are located.