In response to Steven McNicoll's scenario:

It wasn't clear to me from the scenario you wrote whether I'd be
arriving from the north or elsewhere. If from the north, I'd have to
fly the published PT because a course reversal is necessary. So, upon
arriving DEPRE, I'd continue south on the localizer for about 1.5
minutes, and fly any type of PT to the west of the localizer. Upon
returning to the localizer, I'd follow the glideslope down.

If I'm approaching from the south (which is probably what you meant)
and hadn't already arrived at GRB VORTAC before being cleared for the
ILS, I'd join the localizer and:
1) when I'm within 10 nm of DEPRE, descend to 2700 and inform approach
that I'm "leaving 3000 for 2700"; and
2) capture and follow the glide slope.

In my opinion, the PT is unnecessary because there is no course
reversal. Some would probably argue that you've been given radar
vectors because your prior instruction was direct GRB VORTAC.

In this northbound scenario, let's say you weren't cleared to 3000, and
were still at an en route altitude, suppose 6000, when approach clears
you for the ILS. You'd have to lose altitude fast. I still wouldn't
do the PT. I'd instead opt to descend in a holding pattern at DEPRE
(which is an IAF) down to 2200 (or capture glideslope northbound when
south of DEPRE on an inbound leg of the hold). Of course, I'd let
approach (or tower, as appropriate) know what I'm doing so that ATC is
not surprised. If they need the airspace for someone else, they'd let
me know. Doing so also keeps me closer to the airport in case
something goes wrong when I'm descending. I think you could opt to do
a PT instead, but how would you know when to begin the PT if you're
approaching from the south and don't have a GPS?