The significance of the SG prefix is likely to lie also in data
consistency for bus identification.
Consider SBS3000 and SMB3000, if we take only the integers (which is quite
probably the preferred way for machine-reading and identification),
the buses can't be reconciled by the system.
If we begin the gradual process of converting all eventually to
a single prefix, this complication naturally disappears. This
approach is preferable to living with different prefix, and worse,
having the same integers, which is the case now.
I can't imagine Singapor will have 10,000 public buses, so
unique 4 digit
integers for bus ID sounds like a very good solution to me.
That is a good argument for a common rego prefix. However, I am
still unsure of LTA's commitment to the common SG prefix, given
that the latest batch of BSEP B9TL Wrights were registered in the
SBS35XX series, which directly conflicts with SMRT's own double
deck BSEP series.