I already see the answers I got.
at Road Construction from the day/night Watchman
on a street where the houses were still standing but
purchased by eminent domaine for a highway widening I was told
loosely Quoted
"I cannot give you Permission. some of the people who lived in these places are still
upset at having to move. add to that legal issues. But
If I drive by making my rounds, I'm not going to be stopping
to see what your doing

"
Remember though, this was 10 ish year ago .
People were not breaking in places stealing Copper
for a living.
as far as the type of construction your talking.
I would believe the Construction Crew would be the one to ask.
as they would be temporary owners till their work is complete .
that is unless they urge you to ask the land owner.
my guess,
Fear of you getting hurt and blaming them will be your biggest Hurdle.
with destruction & Theft as a distant second.
IF you Introduce yourself openly as you Ask