The seats dont seem to be from the citaros.
Seems more like either of the below from the shape of the
handlebars:
1. Lazzerini Pratico 2845 (Most likely)

2. Those used on the BT shuttles (less likely)

3. Those used on Lion's City (least likely)

Full credits to photo owners: http://hkbric.hkbdc.info, http://businterchange.net, Marek Banach (Wikipedia)
If its the 1st pic, then really a breakthrough towards "HK
style"... 