I think this should be possible, if you don't mind adding a single cable tie or tape to fix the gear cable to the right-hand chainstay, as the braze-ons for the Rohloff gear cable lead down the left-hand chainstay, whereas the Alfine gear cable runs to the right.
I did something similar earlier this year to build up a Van Nicholas Amazon Rohloff frame with an Alfine, which has similar cable routing braze-ons. I used the blue and green Alfine anti-rotation washers and a single cable tie. No other modifications necessary in my case.
