This is a question best asked of Mentor Graphic's support, since the Calibre interface is theirs. I suspect they probably use "hilight sets" to do this, using geCreateHilightSet(). However, even if you knew the name of the variable containing the hilight set, you can find the hilight objects, but you may not be able to find the details of the coordinates as these aren't necessarily exposed in SKILL. Potentially geAddHilightFig would allow you to find the associated shape, but I doubt that's the case because the interface probably doesn't know the source object to highlight - and for many rules it would be gaps between shapes, or derived layers that need highlighting.
Thank you Andrew!
I'll try to contact Mentor