First of all, welcome to the forum, DeanoZ. There are many here that know much about turkey hunting, and the exchange of information and ideas that takes place on this site is often of great value to both new and experienced hunters. Please continue to participate. I will try to answer your question from my own perspective, but I hope others here will give their opinions on this, as well.
Topo and aerial photo maps can be of great value to hunters just about anywhere and with any game, but their value in any given locale is predicated upon the hunter being somewhat familiar with the turkeys, their habitat, and their use of that habitat in general terms. I have stated before that all turkeys and turkey hunting country is not created equally. That is, the things that I would look for on a map in regards to hunting the Merriams subspecies in southern New Mexico are not necessarily the same things that you might be looking for the subspecies you would be pursuing in your area.
Fundamentally, however, the keys to finding turkeys in any area are the presence of four things....food, water, cover, and roosting habitat. In order to solve the puzzle on where to find turkeys by using a map, you must have an idea of the importance of each of those factors in the specific area you are researching. Here in New Mexico, the key ingredients in that puzzle generally are the presence of water and roosting habitat, so when I am looking at maps of an area, I am focusing on those two things first. In your hunting country, those things may be less relevent.
At any rate, you must have some sort of starting "bank of information" regarding the turkeys in the area or region you hunt in order to make educated guesses on where you might find birds in similar areas that you might be looking at on a map.
Having qualified my comments with all of the above jibberish, and to finally get down to answering your question, the key elements I will look for on a topo in most instances are water courses with wide bottoms that would indicate the presence of openings or farmlands (some topo maps will show thick vegetation indicated in green shading and open areas as not having any shading), and also a good mosaic of cover and small to medium size openings (also indicated with shading). In country that has some relief to it (mountains, ridges, saddles, etc.), as you pointed out, those areas are often prone to turkey use, but once again, having some sort of knowledge base related to "comparable" habitat is the key to making sound decisions on how to approach a hunt in any given area.
I actually prefer to have aerial photos (or take a look on Google Earth) in addition to topo maps if I can get them. They make things much more clear in terms of what is actually "on the ground" than just having topo maps does.
(Gee, I hope some of this makes sense)