Suspect:
SBS8316M
(BN SP) 
(BN 518)
SBS6249L
(BN 518) (BN SP)
Okay, what I'm going to post here is slightly confusing. Because
AFAIK, if 8316M is perm Sv 518, it does not directly replace 6249L
(ie. it's not represented by what I posted). It would be replacing
2622T instead (which like I said, hasn't been spotted this week on
Sv 518 at all).
8316M did Sv 518 for 4 days straight though from 04 Dec (Tues),
including today. Monday 03 Dec it was in PSR, but I can't recall if
it was on Sv 15, 17 or 518. But for the other 4 days till today,
8316M has been on Sv 518.
6249L's replacement should be 8248B because that bus
has been stuck on Sv 518 for more than a month while 6249L went MIA
from Sv 518 and did Sv 33 & 222 in the meantime. But I've not
spotted 8248B so far this week on Sv 518 on its usual timings I
spotted for the past weeks...so I need to find 8248B again..
Another thing to add is that despite Sv 518 starting
WAB operations alr, the 2 SP Citaros (6254X & 6272T) are still
cameoing this week on Sv 40, 292, 6 etc. So means the additional
WAB into Sv 518 has to be a KUB..
