regarding the air-conditioning, it may sound like a waste of
money, but it's business sense. they can easily earn back the cost
of installing the air-con from the air-con fare's premium.
furthermore, there would be less complains of not having enough
air-con buses. anyway, Mk II and N113CRB's were the only NAC buses
running around that have at least a couple of years of life.
we have no confirmed news of the O.500LE orders. SBST is definitely
not buying anything other than O.500LE from Mercedes-Benz.
and no guesses where the new buses will go to. 
we can wait till we are sure these O.500Le's are coming before we
answer this.
and dun worry, those O.405's in hgdep are perm. they belong to svc
100 and were x-fer to hgdep from amdep following shift of control
of 100 to hgdep. eventually these buses will move back to amdep,
like many of their former 100 O.405 counterparts. these buses
are:
326L
335K
345G
535R
3826R
3902D
