I believe not. SMRT will do it, not the drivers. I had a bus
driver friend on my local route 913. He first drove on 969 in 2000
and was posted to 913 from 2001 onwards. Some drivers are posted to
a certain bus and must drive the same bus everyday except
sometimes, when your normal bus brokedown before leaving depot,
they can drive a cameo bus. 
For special events like IMF, SBS or SMRT will choose drivers based
on experience, courtesy level, language (can speak proper english),
and driver's record. They don't want their reputation to fall for a
big event. 
