There was a swap involving 976S (ex-AM 800),
1020T (ex-AM 854),
1060C (ex-800 then SP) &
1092K (ex-AM 804 then SP) not too long ago. It's
probably linked to where 976S & 1218R's statuses now. I suggest
you go and find out more from the people who stay in
Yishun. 
I do think 976S & 1218R are SP for this month though till
June Sch Hols are over.
Anyway, 9449G & 7724A's swap is confirmed
with perm stixs? or observation? I know i've seen both buses
frequently too on the abovementioned svcs, just wondering if
there's any new perm stixs for them?
yes 7724A and 9449G is spotted by perm stix...
SMB8008L is on the exact slot of 1218R, who is seen running
around, so it is cfm out.
851 schedule currently is exactly the same as normal wkdays,
with 976S already running arnd b4 the hols started. the only thing
im not sure is that if 8009J is rpl 1568H (not seen recently), with
another habit alr replacing 976S..
so both 976 and 1218 are cfm SP, not just for the hols
Also, 854 has now 5 extra AMDEP buses..
any idea which are not perm?