MK3s used to be perm on 173. SBS819G, SBS820B, SBS821Z, SBS822X
were new to 173.
As for 189, there were also perm. SBS2609H i think
7256 was one of the VO 2 axles perm as well... During those
times I do not remember regos, but there were plentiful of MK3, MK4
Strider and VO 2 axles. Before this was a mix of MK3 and
Atlanteans.
Refreshing my old brain...
TIBS Handover Days/189 Goes Yellow, 2000 to 2003 ~
426M, 517J, 519D, 544E, 592R, 597C, 633G. 988H (S/TQ).
Post-989 Days/Short Bus Era, 2003 to 2006 ~ 516L, 517J,
519D, 520Z, 544E, 592R, 597C, 633G.
Early Articulated Days/Split Shift Comeback, early
2006 ~ 516L, 517J, 519D, 544E, 520Z, 592R, 597C, 633G.
863J, 869T (S/TQ).
The Articulated Days/Going Long, mid 2006 to late 2008 ~
516L, 517J, 519D, 520Z, 544E, 592R, 597C, 633G. 863J, 869T, 1162S,
1224Y (S/TQ).
On the Road to WAB Service/189 Easy-Access Revolution, late
2008 ~ 11D, 12B, 13Z, 14X, 15T, 16R, 519D, 592R. 863J,
869T, 1162S, 1224Y (S/TQ).
516L, 544E and 633G to Woodlands Depot. 517J 597C to spare then to
s75.
WAB Service Days/THE ノンステップバス (The Non-Step Bus), 2009 till
present ~ 11D, 12B, 13Z, 14X, 15T, 16R, 17M, 18K. 863J,
869T, 1162S, 1224Y (S/TQ).
All the era names are my own notes... You can consider using
similar codes for your favorite service.