Literally just watched an internal talk about this topic at work (Microsoft). Lots of cool internal research to make things better in every domain, but as you said, it won't be shared that much.
The Open Compute Project is great though, and MSR does awesome research across many domains too, as does Alphabet.
Was the Bell Labs Systems Journal shared outside of Bell Labs contemporaneously? I have original copies of the Unix issue, for example, but have no idea if that was 'generally available' back when it came out...
Without deeply researching the topic, my understanding is that Bell Labs didn't really "open source" everything or really most things. Just look at the later law suit over Unix.
"Due to a 1956 consent decree in settlement of an antitrust case, the Bell System was forbidden from entering any business other than "common carrier communications services", and was required to license any patents it had upon request. Unix could not, therefore, be turned into a product. Bell Labs instead shipped the system for the cost of media and shipping.
...
In 1983, the U.S. Department of Justice settled its second antitrust case against AT&T, causing the breakup of the Bell System. This relieved AT&T of the 1956 consent decree that had prevented the company from commercializing Unix. AT&T promptly introduced Unix System V into the market. The newly created competition nearly destroyed the long-term viability of Unix, because it stifled the free exchanging of source code and led to fragmentation and incompatibility. The GNU Project was founded in the same year by Richard Stallman."
I'm well aware of the history of Unix. My point was simply that Bell Labs was historically not a particularly open organization outside of the bounds that they were required to be by law.
The Open Compute Project is great though, and MSR does awesome research across many domains too, as does Alphabet.