Hi Ron.
The Walthers Cornerston Utility Poles are about 5" tall (4 7/8" to be exact, at least thats the walthers ones)
Your other question was if it was a good idea to run power for the layout through them. Here is my opinion. I would not suggest doing this at all. Power lines on a layout tend to be hit by hands moving things in and out of the layout. My experiece with stringing lines was not good at all, I got them up okay and they looked great but I found it hard to "steer clear" of them and I ended up ripping them down because of a few acidents and I was fed up with repairing the twisted lines... My layout still has the utility poles on it, just no lines are strung
If you want to string lines, I would HIGHY suggest doing them in the back of the layout and outta the way where you wont bump them or drag them.
Sorry to shoot down you idea, I admit, that would be AWESOME to have the power supplied by working power poles but it is highly unlikely that you will be able to make this happen due to the fact that you will be having to replace/rewire countless amounts of times.
Just my thoughts on the subject, dont mean to sound mean or anything.