WHY?
Firstly, only 51 B10TLs and 12 B10BLEs were procured by SBS Transit, a pitiful number compared to the number of other buses procured by SBS Transit, not counting demonstrator units. As such, it wold make no sense to distribute these buses around the island, across multiple depots, when they require parts that are not common to other bus types. As such, to ease maintenance and repair of these buses, SBS Transit concentrates each type to just one depot, with B10BLEs being deployed on routes which use BBDEP as their depot and B10TLs deployed on routes that use BNDEP, BRBP or AMDEP as their depot. Its economies of scale. As such, it is extremely rare to catch these two buses together as they are almost always on opposite sides of the island.
At least, this is my theory. If anyone has a suggestion on the occurence of this scenario, do feel free to share here

