tall service mast for remote aerial drop
It's probably unknowable whether or not that 8x8 post is capable of supporting an 18 foot lever, er mast, attached to it. What is the strength of the wood? How deeply is it set in the ground? Etc.
Will the telecom make any requirements as to the materials of the mast? Steel tubing and pipe can often be had in continuous lengths up to 24 feet; you could set one of these in the ground and let it be your mast.
This seems like a lot of trouble to make a drop spanning only 30 feet.
I presume you're wanting that 30 feet aerial because it crosses something that can't easily be trenched -- a driveway, perhaps. I'd find a way to make the crossing underground and let the telecom attach conduit to descend the utility pole and meet with your underground conduit.
Underground construction can be soils dependent, but some techniques I'm familiar with are these:

Hire a contractor to bore a hole with a pneumatic piercing tool, commonly called a &quot;missle&quot; or &quot;mole&quot;
Bore (erode) a tunnel manually with running water, either directly from a hose or with the help of a pump eg pressure washer
Cut-and-patch: saw cut the pavement, trench normally, then backfill and patch