Connecting a N.O. grounded switch to a scanning switch matrix
If you could change your scanning code to either pull the column high, instead of low, then you don't need to do anything special to read this switch. Connect the column input to R2 and read the switch from the junction of R2 and the switch. You'd also want to enable the internal pull-up resistor on the column inputs, instead of the row inputs.

If that's not possible, then your circuit should work. Be sure you tri-state the column, rather than pulling high, otherwise you might reverse-bias the base-emitter junction too much and Q1 might not like it. You could also use a PNP for Q1, which will invert the logic (I think you want that anyway). In the PNP case you can also dispense with R2.