BMTC - S1 Route (Vijayanagar to Vijayanagar)

Saw these buses plying on outer ring road near BTM layout yesterday & today.

Looks like an extension of Big10 concept, Big10 to Circle Routes to S (not sure what it stands for) routes?

Surprisingly, while the BMTC call center did not have any detail to offer, the buses seemed to quite fully loaded!. I got bumped from the call center guy to the control room to Vijayanagar Bus Stand (22952362). All were cordial, willing to help, but had no info to offer.