I believe when SMRT bought over TIBS. there was a part in the
article which wrote that they would preserve the TIB plate for
new buses as memory for its milestones of the past.
now they go bacjk on their word.
Just after SMRT took over Tibs in 2004, 10 buses from CSS were
transferred over to SMRT (9 CAC Nissan UDs and 1 UMW Lance). They
changed to TIB plates after the transfer.
However in 2006 when more CSS buses were also
transferred to SMRT, the CSS plates were maintained instead of
changing to TIB plates. Same for the transfer after CSS wind down
in 2007.
And for now SMRT bought new buses and decided to use the new SMB
plate instead of reusing the TIB plates.
Whereas for SBS buses, they have been using SBS plates for over
30 years since day 1 
