Doesn't a color tinting on a texture cause a state change as well? In that case I wouldn't gain anything if I'm not mistaken.
It depends if you are drawing them in sequence (with the painter's algorithm) with other tinted textures. Remember 'tinted' state is either a color or alpha != 1.0.
So you could batch a bunch of color tinted textures into one draw call. If it was a specific heatmap layer just setting alpha = 0.999 on the parent of the heatmap layer would get all tiles (colored or not) batched in one draw call (ie everything is tinted = true) (even the bitmap font text)
If instead you meant the heat map came from individual button backgrounds getting tinted with color then you could test whether setting the parent component to alpha = 0.999 (a trick that could cause performance issues on certain older devices) was acceptable.
Of course if you had a finite set of colors used you could pre-bake those color swatches into the atlas without needing tinting at all, or use the single base texture white version of the texture, and work on setting colors arbitrarily (or alpha = .999) to try and make everything be batched together with tinted state = true.
You might want to just test on the older devices you support (like the iPad1) comparing whether you see 200 drawcalls performing better than the alternative scenario of alpha = 0.999 parent trick with 1 drawcall.