Ask HN: Can a VoIP provider hear an analog phone that's on the hook?

Electronically (i.e., legality aside), can a consumer VoIP interface (e.g., Ooma Telo) potentially listen in on an analog phone when the phone is on-the-hook, or is the phone's mouthpiece/microphone guaranteed to be inoperable by design for all phones, even the simplest all-analog models? Perhaps with enough gain, DSP, clever circuitry well beyond CMR, and so forth?

If so:

Do wiretapping laws prevent snooping on this single-party situation, and are they enforceable enough to be effective?

Presumably a PSTN CO could do the same, but I assume oversight is much tighter in that case, and I figure the chances of eliminating noise are immensely higher when there's a Linux box (or whatever) right on the customer's premises a few meters from the phone, rather than a long copper run to the pole and beyond.