>> 1. Is the sort of thing ever outsourced to, for example, India? Or wherever else is a common place for call centres if it’s no longer there

I don't know if there are call centers full of phone sex workers. You'd have the same background noise you get when calling any call center. And the workers would have to get paid when nothing was happening.

Here's a read on the topic:

https://www.businessinsider.com/reality-of-being-a-phone-sex...

>> 2. Is anyone currently doing this with chat bots and speech synthesisers?

Me: Hey Google, talk dirty to me.

Google: Manure. Dust. Crusty crumbs on the floor. <Poop emoji>

I can only report that Google does not talk dirty to me at this time.