Guillen's work is notable because he helped Mercedes-Benz parent Daimler develop its own test version of a plug-in truck before joining Tesla in 2012. Daimler is a big player in the field, and its entrant in the US Department of Energy's Supertruck program, which debuted in 2010, got a fuel-economy average of 12.2 miles per gallon, which was double the DOE's goal for the program.
Musk first publicized Tesla's intention to develop electric trucks last summer when he unveiled the company's second-ever "master plan," saying that early versions of both electric trucks and buses may see the light of day sometime this year. Shortly after that announcement, Mercedes-Benz introduced what it called its Urban eTruck. That model has a single-charge range of up to 124 miles, which would make it a prime candidate for municipal use.
Meanwhile, others are also joining the fray. Nikola Motor Company (as in, uh, Nikola Tesla, though there's no financial relation to Tesla the company) is working up its Nikola One, which the company hopes to have in production by 2020. That model is said to be "zero emissions" because it's propelled by a combination of a lithium-ion battery and a hydrogen fuel cell that is estimated to give the truck a range of up to 1,200 miles. Additionally, Toyota obliquely implied last year that it was also working on a hydrogen fuel-cell semi-truck project.