Good question, if on the T-Mobile coverage map an area has "5 bars", does that mean a site is there? It's weird, right where there's 5 bars theres usually a water tower or a non-broadcasting tower, does that mean there's a T-Mobile site there?
Generally, yes, that means a cell site is nearby. Look for the triangular green blob pattern - since most cell sites have three sides, in the center of the green triangle you'll ususally find the cell site.
They are not triangular icons. On the map, the signal strength will often propogate in "triangular" directions away from a tower site. Generally, in the middle of these "triangles" is where the tower would be. There is an example of such a situation attached. Hope this helps.