I hope this google assistant will start talking to them while it waits for you to notice the notification, essentially putting them on hold until you answer.
Didn't look into it so no idea how it behaves, but sounds like a realistic solution to this problem and would have very interesting consequences!
The most likely interesting consequence will be companies burying a line in the ToS saying they can deny you service if you use a tool to reduce your opportunity costs of sitting in a hold queue.
The purpose of a hold queue is to reduce the number of customer service calls a company has to field. They will not take lightly to any service which defeats this.
Alternatively, they'll hire staff to answer the phone, say a few words to break out of Google's hold music detection algorithm, then put you back on hold, this time with ads instead of music. Repeat every few minutes to make sure you're still stuck on the line.
There's no limits to what's possible when you realize the purpose of anti-customer service is to harm customers rather than help them.
They could, but google could pretend to be you and answer basic questions until you pick up. Or just pretend to be your secretary. We're at a point where it becomes impossible to tell if you are talking to a human or not, at least for the first 10-20 seconds. I don't think those companies/call centers can win here, they will have to adjust sooner or later.
Didn't look into it so no idea how it behaves, but sounds like a realistic solution to this problem and would have very interesting consequences!