I have a pole building shell and I plan on using a heated slab foundation and creating a house/barn in Central NY.    Please advise on slab specifications.  Opinions vary to a large degree about whether the edges need to be thickened or not.

If you are using the slab as the only foundation, you need to thicken the edges, as well as under any load bearing walls. You have to think of your slab edges as beams, because when the ground under them inevitably settles a little bit (even as little as 1/4") in a few spots, the slab will either span the distance or crack and fall the distance. Remember that the strength of a beam is approximately proportional to the width times the depth cubed. That means going from a 4” non thickened slab to a 4” slab with 12” thickened edges will increase the strength by about 3^3= 27 times. You also need to put in low and high rebars on the edges, to strengthen the tension flange, which will switch across the slab depending on how the dirt settles. Don't waste your money putting rebar right in the middle of the edge. The same goes for under any load bearing walls.

I am currently living in a 4” thickened to 12” monoslab house. The whole slab only has 2 hairline cracks that developed about (2003-1984)= 19 years after the house was built, which I consider acceptable.
I will be constructing my next house on the exact same foundation.

Thank you!  If you have time, please address the pole building part of the equation-- do I extend the slab out side of the dimensions of the pole building or just to the board and are the poles isolated if so, with what material?

I need to know a few details to advise you. Do you have a link to a diagram of the building, or a picture of one in construction? What kind of siding will it have? Is the siding right on the outside of the poles or is there something between the siding and the poles, or is that a decision you make? How is it reccomended to attach the poles to the foundation? What are the poles made out of, and what diminsions are they?

siding is larch, yes, attached to the poles with vaproshield b/t poles are pressure treated and 6x6 in the ground area is shallow to bedrock/shale soils are Lordstown Channery elevation is 1980 feet. Site is a hayfield on top of the hill

A couple of questions.
How deep are the foundation columns set in the ground? Do they extend below the frost line?
If the foundation columns are below the frost line then the building itself should be stable and not subject to frost heave during cold weather. That should also eliminate the need to overly thicken the edges of the slab, especially if you only have one floor of living space, or if the barn has a second floor (loft) already in place, as the weight of the building and any live loads it must support are carried thru the columns and are not supported by the slab. However, if you are adding a second floor, the live and dead loads must accounted for, and may require piers or thickened edges, depending on the structural design.
Also,have you discussed this with the local building codes people, or do you have to? If they do get involved, then they will have the last word, no matter what.

Wes is right, if you are setting colums for the posts to carry the load of the building, you don't need to thicken the edges of the slab as much. I thought the slab was the only foundation, aka the posts were setting right on top of the slab.