I have done this from more than one Modolo brake pad holder. The old Modolo brake pad holder have such a pretty delicate look to them that I wanted to preserve the appearance without using those horrible old pads that could easily eat through a precious classic rim. I can't remember how I did remove the pads except that I remember I didn't have to destroy them to do it, however I tried to find replacement blocks in a more rim friendly material. I gave up trying to find them and then decided to cut my own brake blocks out of some new LBS type pads. I was able to do it, but the pads kept popping out so I decided to use some other holders completely.
Garth Libre in Miami Fl USA