The two UK businesses have already struck a deal in Hong Kong, where 23 trial vehicles have been fitted with the ecoNOxt system.
The product uses diesel particulate filter (DPF) and selective catalytic reduction (SCR) technology, enabling older vehicles – Euro 4 and earlier – to operate to current emission standards.
Green Urban's Nigel Standley says that the two companies can "open doors" by working together.
"We have always known we had great retrofit products and the bespoke engineering ability… However, we don't have the longstanding relationships with the bus companies that Leyland Bus Parts has," he explains.
For the Hong Kong project, an engineering team visited the city to collect data on temperatures and duty cycles.