Ok, the Keyboard, is comprised of 3 columns, the two outer columns have 5 switches each, and the center column has 4 switches. The switches are all lights.  Pins 1 are white, are lamp Ground, pin 8, gray are lamp power. One side of switch is jumpered together, pins 3 & 4, and there  is a black  wire attached as well, which makes this switch effectively a SPDT switch.

KBDTGT
123
456
789
CLR0ENT

If you look down at the switch and hold the jumper (pins 1 and 2 ) on the right side, also has the black wire. The top is the normally open side, has a yellow wire on it, so when the switch is depressed it closes. The bottom is normally closed, and has a blue wire on it.,so when the switch is depressed it opens.  There are two connectors W5P1 & W5P4 coming from the switches. So there is the quandary, there are two ways to skin this cat (keyboard).

W5P1W5P4
151413121312111098
BlueYellowBlueYellowGrayYellowYellowBlueBlueGray
Cut

Overlay

Power

A) wire each of the 14 switches to an input on a MCP23017, when a key is pressed a interrupt is generated and read the expander. Done.

B) Don't screw with the keyboard any more figure out the rows and columns a originally built. Rows go to one half of the MCP23x08 the Columns go to the other then you need a scanner, that is triggered by a keypress. Microchip has a application note  AN1081 

C) And lets not forget you can also achieve similar results as A) by using 2 7-bit priority that are cascaded.