Well, what seems to work for sure is earning EVA miles on UA. EVA announced it and UA's system takes EVA's number.
What is not certain is the other way. UA's website announced it but EVA's system does not take a UA number.
Redemption requires you to call a special group in Houston. The chart is bad and cannot combine with other airlines, including UA. For example, 100K for US-TPE in Y, 110K in Premium Economy, 160K in Business. The agent said availability is hard to find and the availabiltiy is not real time so things are not usually confirmed immediately.
This is the old CO/BR redemption rule, not the Star Alliance chart. Apparently even though the CO/BR relationship ended 12/31/2011, the redemption option never went away.