Yes, lots of tech jobs have migrated from 128 to the city over the 10 years that I've lived here. There are still a lot of jobs on 128, and those companies run shuttles from the city out to the offices for people who live in the city.
You're also correct about the shuttle buses. Those were unheard of when I first started working at a computer company on 495 in the 80s. Boston and Cambridge, as well as attitudes about city living, have changed a lot in the past 2-3 decades.
When I first moved back to the area after grad school, some people I knew lived in the city but not many. It certainly wasn't the norm.