My understanding is that the CVL could never be fully electrified. There are listed structures on the routes that cannot be altered like the Caerphilly Tunnel, and there are neighbouring Cardiff University buildings that contain extremely sensitive equipment that would be negatively affected by the installation of OHLE through the stretch of line beyond Cathays station.
And yet at one point "proper" electrification was being seriously considered, wasn't it?
I haven't seen the suggestion before that Caerphilly tunnel is legally unelectrifiable, just that it would a rather expensive undertaking.
And I find it difficult to believe that if full electrification were being planned the University would be able to stop it.
I think the Delft University of Technology in the Netherlands did have a hand in delaying a tram extension to and through the campus on interference grounds, but that's a bit different.
(The problem was apparently solved by the physics department figuring out a way of doing the wiring to minimise electromagnetic interference, though what works on a relatively low voltage DC tramway might not be so suited to 25 kV trains).