The german X1 forum found out:
These adaptors are for an
ADDITIONAL WATER PUMP for the heating.
Do you remember, in earlier models bmw's climatic control panels had a "Rest-knob"...the engine has'nt to run and once activated these pump circulated the still warm cooling water through the heat exchanger.
It seems that there a configuration exists where that pump is still build in. I know from a xDrive 23D and a sDrive 18i.
On the part of BMW for these 3 holes is no solution in sight. So to prevent dirt to enter the engine bay, take duck tape and fix it.
(sorry for my bad english)