The batch that the 453 used to have were indeed the newer generation of the Citaro Gs.
ML29: My understanding so far is that the L94UAs are due to stay on the X66. The Citaros are intended to go to the 58 (or so I heard) to cascade the rigid Citaros to the 56 to replace the Scanias. As per October I have already seen a few Citaro repainted to orange (the branding for the 56).
What I heard is that there will be 18 Citaro Gand 14 of them will go 58, and the remaining will go X66,
just some of them will be converted to dual door,
while the cascaded L94UA will go 58 in Gateshead.