The Google Wallet app will let you import any pkpass file. The trouble is that most websites that support the format will only offer them for download of you're coming from an iPhone.

Google's format also has a download option but that format doesn't work well for desktop users, so Google prefers to import via the web.

One annoyance I've faced is that Apple Wallet will not accept a downloaded file, or a file transferred from another app. You must click a link in Safari or it will refuse to load the damn pass.

I'm surprised how terrible all of these major wallet apps are at handling the slightest of edge cases.