Already popular in Hong Kong and the UK, SBS Transit placed an initial order of 150 Euro V B9TLs (Batch One) as parts of its fleet expansion and renewal in August 2009. A second order of 300 units was made in September 2010 (Batch Two and Batch Three). A further third order was placed for 550 more units in July 2012 (Batch Four). On 1 July 2014, SBS Transit placed a forth order for 415 more units (Batch Five). The bodywork was the second generation Wright Eclipse Gemini II that was supplied by Wrightbus of Ballymena, Northern Ireland. However, unlike the orders from other bus operators the kits were delivered in CKD (complete knock-down) form and then assembled by SBS Transit's technical counterpart, ComfortDelgro Engineering. According to Belfast Telegraph, Wrightbus described these WEG2 orders along with those from Hong Kong to be a "lifeline" during the period of 2009-2010, when the company was facing a domestic economic downturn.

First introduced in late 2010, these buses were powered by the Volvo D9B310 EC06B engine (9,364cc) which is Euro V compliant with the use of Selective Catalytic Reduction (SCR) technology, requiring the use of Adblue. The initial 150 units (Batch One) and the final 415 units (Batch Five) were fitted with the new generation 6-speed ZF EcoLife 6AP 1403B automatic transmission. The second and third delivery of 300 and 550 units respectively (Batch Two, Three and Four) were fitted with 4-speed Voith D864.5 automatic transmission.

Air-conditioning was initially supplied by Eberspächer Sütrak for Batch One to Three, and its R488 model was a custom product newly designed to meet SBS Transit's requirements. Batch Four and Five units had their air-conditioning supplied by Denso of Japan. The B9TL WEG2s received either Hanover Displays EDS (Batch One, Batch Two, SBS3189X, and later Batch Four) or LECIP EDS (Batch Three, early Batch Four, and Batch Five). From Batch Three onwards, Wright-bodied B9TLs registered in the 3000s range feature a full low-floor configuration on the lower deck. Batch Five units are registered from SBS1Z onwards had revised interior features including a straight staircase and headrests on side-facing priority seats (similar to the Volgren-bodied B10TLs).

With orders totaling up to 1,415 B9TL WEG2 buses for SBS Transit and expected to be fully delivered by 2017, this makes SBS Transit one of the largest Volvo B9TL operators in the world.

In December 2015, Land Transport Authority bought out SBS Transit's contract for any remaining B9TL WEG2s yet to be delivered. Together with the BSEP fleet, they are reassigned to other operators in preparation for the Government Contracting Model (GCM/BCM).