Can I Interrupt on any keypress on this keypad?
No, you can't. Owing to the fact that you have to manually cycle through each row (or column, depending on which way you are holding your head at the time) in order to read which keys are pressed there is no way to relate a button to an interrupt.

The only possible way would be to use an external keypad interface chip (you could roll your own with another Arduino) which has an interrupt signalling facility in it.