Linemen will always ground a transmission line before doing any work on it, unless live work is authorized, and then other safeguards apply. They never assume a line is actually dead just because it's supposed to be dead; they always assume there might be a backfeed or other source of potential on the line.

The balcony solar rigs (at least the properly designed ones) don't energize the male connector until they detect that it's plugged in. And they de-energize it if the mains/utility power goes out.