Even zip tied, you need a tool to remove them, so that meets my definition of permanently attached to the bike. Not to mention you'd need a new zip tie to reattach them.
I work on bikes as a profession, so I have installed many Wald folding baskets. I am glad you are happy with yours, but the last bike I worked on that had one (which was just a couple of weeks ago), the basket was difficult to fold and unfold from bits getting bent and the metal clip meant to hold them folded was rusted and no longer functional. Of course it depends on how you take care of stuff, but most people don't, so I get to try and fix these kind of things on a regular basis.