Wayne: Welcome back to this great hobby. As far a using a replacement for homasote board, I am unable to locate any here on the west coast of BC, I have used a product called dona cona board for many years, it is a type of press board made out of paper and cardboard, I have had no problems with it warping or swelling, even with all the glues and water based scenery that has been added.
It comes in two types, make sure you get the natural type it is lite tan in color. The other is darker color and has tar either inside or on one side, not the product you want. I just put it down over the plywood with one inch screws. If for some reason you have glued something down and want to pull it up it comes up very easily and it will only bring up the top layer of paper product, leaving you lots left to work with. It takes a little bit of work if you go slow with a sharp knife but cuts easily with a jig saw. I bought some for my expantion not long ago and paid $8.00 (canadian) for a 4 x 8 sheet.
I use cork for my main lines and sidings with flex code 100 track, I find that with a little paint on the ties and rail there is nothing wrong with it, and also everything runs on it. Also I have enough of it and can not justify the expense to go to 83. For my engine service area and industries I hand lay my track. I use micro engeneering stained regular ties and small spikes. I glue the ties down and give them a little sanding on the tops to remove just a little of the dark color then add whatever stain I wish, usually oak and driftwood, you can add as much as required. I have also handlaid my track on the cork, just glue the ties down and then spike the rail down. As far as using pliobond, I have tried it a few times with out sucess, seems I either get the heating method too hot and burn the glue or not hot enough, after a short period of time it lets go, so have stuck with spikes. I have spiked rail down on my bridges also without problems.
I have never heard of ties pre glued to cork roadbed. I would take a few lengths and curves an practice laying the ties, I made my own jig one side is for regular spaced ties and the other end for industrial spacing, and putting the rail down before you go out a purchase a large quantity of ties and rail, it takes a little in getting use to and it does go slow. As far a spiking the track down I go every third tie spike down the rail and every fifth tie spiking the rail down on industrial or sidings. Depending onwhat you are running and tightness of your curves you may have to adjust this.
Good luck and enjoy.
Ron... Abbotsford, B.C.