Yes.
When dealing with a voltage like 34.5kV, the earth path has a low enough resistance to be an effective (although not particularly pleasant in its side effects) fault clearing path. That is, when you calculate the resistance of the ground electrode attached to the wye point of the POCO transformer and the resistance of your GES anywhere at the load end,
they will allow enough current to flow to trip some sort of OCPD within the utility. Until that trip happens, though, the voltage on the ground system relative to remote earth can get pretty high.
Your thread title says that it is a grounded system. You know this, or assume it to be true based on the presence of a wye transformer with a visible ground electrode or primary neutral connection?
As long as all of the actual loads on the campus are derived from transformers with ground electrode and in most or all cases neutral connections, the nature of the 34.5kV service should not affect you.
As far as surge protection and OCPD on the 34.5kV system itself, I know so little about those voltages that I should not make any statements at all. That much I do know.
Last comment: On the primary side of a three phase transformer, with
delta input, it would actually be harmful to run and utilize a neutral even if the primary supply was in fact a grounded wye.