Yeah, a VPN or even a free bridge blocks this attack, assuming LE hasn't enumerated all of the bridges. China did, but the Tor people detected it. I have not seen them mention that they detected anyone else doing it. Of course, maybe others are just better at doing it surreptitiously, or the Tor Project was served an NSL, oh my. Most likely, Western LE don't care enough about Tor users to do it. Obviously, since this attack has not been performed as far as we know, they don't care about SR vendors enough to do it. Stealth packaging and safe shipping operations are far more important for vendors. Don't get your fingerprints on the packages, change your mail drop locations, don't carry a mobile phone with you, that kind of stuff.