I have a situation where my 3/4" plywood sub floor has to butt up against pine T&G flooring that is a little less than 3/4" in thickness - there is nothing I can do about it. My tile guy is going to put tar paper, wire mesh and a 1" thick mud floor over my sub floor and this wood floor area. I am anticipating he would like these areas level; how/what material should I use to do this? I am concerned that the mud floor will not fill in the gap because of the wire mesh keeping the mud from completely filling it. Are my concerns warranted? What should I do?

If I understand this...

You could use a floor patch compound and feather it out to say 12" wide to blend the difference in so that when 2nd layer of plywood installed there is no difference...

BUT, if wire mesh and cement are being poured then I really wouldn't worry about it... I'm sure the cement will fill in the difference nicely!

Thank you very much; yes, 1 inch min mud floor is being poured so I guess I am in good shape :)

Good luck!