No it doesn't. That's why you shouldn't market products with the claim to make secure calls to her.
There are product to encrypt PSTN calls. These products needs to be used at both ends to be effective.
> If end to PSTN can make it more expensive for the NSA to collect, then it's good,
It doesn't, that's the point. You can count on the whole SS7 being compromised, all the time. It's where these agencies came from.
> If the default config for apache were to generate self signed certificates, you would say, that's useless, because MITM.
Again words in my mouth. I believe it is in fact the default in the major distributions, and it isn't "useless". This has absolutely nothing to do with the PSTN so I won't discuss this particular straw man further.