SBS8990R
(SLBP 181 
SLBP 174)
SBS8056M
(SLBP 174 SLBP 181)
8990R had been doing sv174 for about three months now (first
seen on sv174 in end April) or most likely when it received the
Paul's Milk advert. The Paul's Milk advert has since been changed
to a new advert about a Gillette shaver. Didn't see it on sv174e so far so I doubt it
has anything to do with 174e.
The replacement bus that went over to sv181 is most likely
SBS8056M, which was spotted on sv181 last Sat. However, I only saw
SBS8056M on sv181 once so far, so I do not dare to confirm the swap
outright. Other users here can help to verify if SBS8056M was doing
sv181 for the past few months after SBS8990R went to sv174.
Have seen SBS8056M doing 181 quite often recently.