It works, if the data has been downloaded from the satellites. This can take a while, depending upon your reception. There is a purism repository that can speed things up, ‘git clone https://source.puri.sm/snippets/1207.git’.
I did that and ran the agps.py script, then I started Maps and let my phone sit outside for ~15 minutes. Then I was able to get an (highly) accurate fix.
You can do the latter part without the repository (i.e., run Maps and let phone sit), but in my case that always seemed to take too long for my patience.
NOTE: When you lose satellite signal, your location will go back to whatever it relied upon before.