Yeah, if it is a RF signal then several stratagems can be carried out to detect the signal and enable counter-measures. With enough hardware i believe i could rig a simple device to do that (although i would never personally try it out on a live minefield).
However if you read the article it says that the Russian device sets the mines off as they are being set. Not after .....but actually as the Chechyan sits down to set the mine. It is not meant to detect RF signals, nor to triangulate on mines (an adept physics student could easily come up with a concept to pick up RF signals ....but that is not what this device does). It actually somehow detonates the mine as it is being set ....meaning that it need not be located plus it kills the person who was trying to set the ordnance with his own mine! Two birds with one stone.
That is by far more complex than simply 'detecting' a RF signal. And the device seems to be working perfectly.