I would rehink the used telephone poles. They are probably already half rotten. Start with new material. 4x4 are too small in my opinion. You need at least 6x6.
This is a good point - some of those poles are good for over 50 years underground. Shove a screwdriver into them to see if the wood is still hard. If so, you can tar the below ground part. But, using a new 6x6 is the easiest way to go.
If you decide to attach it to live trees, I have written books about that since it's what I do for a living. If you're interested in the hardware I use to attach to trees, check out my website where I sell treehouse bolts. But to be honest, for what you are doing, I wouldn't attach it to trees, posts are more reliable over time. Are you going to be hunting out of it or really living there?
I'm thinking something like a tree house like what Tarzen and Jane lived in, and a swinging vine for a quick exit. Now if somehow you could get those shortened telephone poles in the tree as high as you could get horizontal. Then you could run your 2x6's for the floor joists. You just might be able to talk her out of that prayer meeting to come take a look at your home in the sky........no rent, no running water, no electric bill, just a lantern and a double sleeping bag. What more could man ask for?