There are some private buses I've seen that (from signage on them, no deep knowledge) I believe are full of tech commuters. But Austin doesn't have the same tight bottleneck that a place like SF does, where owning a car is an amazingly expensive thing to do, and the Google / FB / etc. buses are a major factor in where people live, etc. In Texas, generally, and even in relatively-speaking expensive Austin, car ownership is the norm among adults, and at least *a* norm among students (dunno percentages -- I wonder whether most UT students have cars).
Cap Metro is better than nothing, but doesn't impress me much or often. Some drivers are great, and I don't envy the job -- but the management does not impress me. (I don't mean how they act at meetings -- no idea -- but management in the sense that routes seem poorly chosen, the route-finding website is poor, esp. compared to the kinds of cities to which Austin likes to be compared (SF, Seattle, Portland), signage is terrible, and schedules are often more in the breach than the observance. And quite a few of the Austin bus drivers -- the ones that I think of as the norm here -- would be correctly viewed as rude, unfriendly, unhelpful, misinformed, and poor drivers, compared to the ones I've seen in the three cities just named. Maybe it's just the PacNoWest air that blessed that part of the country