i have not seen that .. i have seen utility to convert bmp (bitmap) to protel file .. but it could be way fory you .. just save gerber as bmp (layer by layer)
and convert .. maybe you can import protel file ;0))
gerber to powerpcb is possible but u will lose some paramters durring conversion process
u can use cam350 for conversion by creating netlist and so on....
but it is not a good suggection since chances of hidded error