6721P possibly perm AR 16..seen on weekdays and also on
weekends. 6722L might be perm BB 175 as well but I have not seen
this bus as often. Will check on the latter..
on the other note, 6100G has been on sv159 very often now. And
1996X does not seem to do 159 anymore.
SBS6722L might be replacing SBS2771X, since the latter has gone
to some ARBP service... On a side note, SBS1977B still 159 perm,
has cutout of an old 159 service guide (the SBST livery scheme one,
not the current one) at the front... So it's not out, if I'm not
wrong.
