"The Idea Factory" is a great book about Bell Labs, it doesn't talk about tax breaks or subsidies as much as the need to provide some kind of public benefit to stave off the anti-trust regulator. Which is why they basically gave away the the transistor and the semi-conductor. The Bell system also had a LOT of money, kind of like the Google of their day, so they could fund "moonshots"

"Dealers of Lightning" is about Xerox Parc and is also a great read if you're interested in the subject.

I don't think the level of tax breaks has really changed between then and now for R&D, though maybe reducing the headline tax rate reduced the benefit of them? But I think the main issue is that the money wormhole stopped working - Industrial research labs seem to be a kind of luxury good