Software Serial and multiple shields for Arduino Uno
SoftwareSerial can use any pins. That's the whole point of it. However, some shields are wired to use specific pins. If two shields try and use the same pins then you can't use them together. Not stacked, anyway. You will have to use flying leads, or physically alter the shield (cutting tracks, soldering in "bodge" wires) to use them together.

That said, though, you can only use ONE SoftwareSerial port reliably at a time. That means, regardless of what pins they use, you can't use two shields together that require pins other than 0 and 1 (hardware serial). 

To use them both you will need a board with multiple hardware UART ports and modify the shields (as mentioned above) to use the correct pins for those UART ports.