Dr. Caldwell described the mobile lab is solar powered so they never have to stop which implied it is equipped with electric motor instead of combustion engine. But when Sgt. Parks went to the driver seat, he couldn't crank start the engine. Later, Sgt. Park repaired said engine and it starts like a diesel engine.
Just because the lab is solar powered, it doesn't mean the truck is. The sergeant says the fuel line was damaged. The scientists in the lab never have to stop working or run the engine to do their work. It doesn't imply an electric motor to move the vehicle.
Whilst the movie was filmed in 2015 the panoramic shot of central London containing the 'Gherkin' also shows the old building at 20 Fenchurch Street, which was demolished in 2008, its replacement, the 'Walkie Talkie' was completed in 2014.