Reviving an overdischarged NiCd 12v battery
Possibly.  You first need to check each individual cell to see if it is shorted.  Shorted NiCd cells are the most common failure when they are allowed to remain fully discharged for long periods of time.

If you do have shorted cells, do a Google search for "NiCd zapper" or "nicad zapper".  This is a very simple apparatus consisting of a large, low-voltage capacitor and largish SCR.  The idea is to burn open the dendrites causing the short inside the cells.

Then start putting charge into each cell individually.  Anywhere from 100 to 250 mA is good to start.  Continue charging until the terminal voltage gets above 1V.

Do each of the cells as I have described above.  Once all the cells have some charge in them, put the entire battery pack on the charger and see what happens.

If you had an appropriate charger and enough time, my preference is to actually do a rejuvenate cycle on each individual cell.  However, this process takes a lot of time and you have to do each cell individually.  Even if you have a multi-cell charger, that means doing one cell at a time unless you split the battery pack apart into the individual cells.

I've had good luck recovering dead NiCd cells this way.  One word of warning: the dendrites that cause shorts will begin to grow back if you allow the battery to discharge deeply.  Always keep the cells charged.