Looks like Google’s partnership with HTC for free Google Drive storage on One Max was not just limited to just one device. As per Google Drive offers page, selected 2013 HTC smartphones will be eligible for 25GB of free Google Drive storage (in addition to the already available 15GB for every Google user) for two years after the Sense 5.5 update.
We right now know that at least one of these devices is HTC One and it has already started getting Android 4.3 with Sense 5.5 update in a few European countries. So, if your HTC One has got Sense 5.5 update, you can grab free Google Drive storage from your phone’s Drive app now. You can read about the whole procedure here.
There is no word on other eligible HTC smartphones at this moment but One Mini is probably going to one of these devices.