My company needs to secure the proper work permit for one of our employees to complete the installation phase of an engineering project. The plant is in Ontario and is owned by a large, US-based manufacturer. We are also a US-based firm. He will only need to be in the province for about 10 days. What is the proper Visa to secure?

An online assessment would be better able to determine the requirements. However, based solely on the information supplied, it would seem that a Labour Market Opinion Confirmation would be the necessary first step, and a work permit thereafter.

I'm a bit confused by this. If the contract is awarded what benefit can come from the Canadian Government blocking fulfillment of the contract by not permitting a US worker to enter? In the situation that I find myself in, an LMO would seem to be purely subjective and would likely not factor in the work overall cost to contracting company. There is no employment at stake, simply a contract for which my company is the preffered vendor.

Is an LMO the most likely path?

Canadian companies and individuals are free to engage in contracts as they desire, but work in Canada is governed by the work permit regulations. There are situations in which this may include admissibility under business visitor provisions, but there is insufficient information here to determine that this is applicable.