You were quite right that in the way Mozilla are using this, it's suited to speech to text, but running it locally is actually a reasonable way to record a single speaker set of data for use in TTS training.

That's exactly what I've been doing recently, and using it with https://github.com/r9y9/deepvoice3_pytorch/blob/master/READM... is providing reasonably good results - it definitely has my intonation (if somewhat crossed with a Dalek!!)