Is there any chance miles accumulated on EVA prior to it's joining STAR ALLIANCE will be applied retroactively to one's STAR account?

Too much to hope for? Anybody?

Should be, at least some. They can't just delete them and tell you tough luck, start again.

Is there any chance miles accumulated on EVA prior to it's joining STAR ALLIANCE will be applied retroactively to one's STAR account?

Too much to hope for? Anybody?

Are you an Eva Air Infinity MileageLands member? Or are you a member of a Star Alliance airline that took a flight with BR before they joined Star Alliance and hoping to get the points credited retroactively?

If A then you'll be able to submit a retroactive claim and once in your Infinity MileageLand account you can redeem them for other Star Alliance partner airline flights.

If B then you're highly unlikely to have success in a retroactive claim, unless you strike lucky with the person processing your claim and who isn't aware of the joining date of EVA Air and goes yup their apart of Star Alliance now, claim approved. Highly unlikely.

Not likely.

The only chance of having the flight credited to another *A partner is If the points were not credited, and the flight occurred after the official announcement of membership.

My experience has been that when you have miles on a carrier that joins Star Alliance, you keep those miles and your elite status (if you have elite status), and your account then becomes part of the Star Alliance programme.