Hi
For interest
I did have a quick look at T9- Business Jet registrations but couldn't see any current ones
E7-SBA was T9-SBA Citation 1
D-HAVD was T9-AAO EC-120
E7-AHA was T9-AHA Jetranger III
E7-SMS was T9-SMS Citation CJ1+
I'm not sure about military registrations but there was a Jetstar 6 registered T9446 (S/N 5046 now stored and probably ready for scrapping) which suggests the T9**** registration may exist but not in the format you had seen, two numerical followed by two alphabetic characters.
Sorry can't help much further
M.E.