I've been on a lot of company tours over the years in a wide variety of industries. A few of the vineyards and breweries that had regular public tours were fine with photography but I can't recall any other industrial facilities that allowed public photography. Even when going into plants as an employee or as part of a trade association tour photography was usually restricted. Some of the high tech companies required cell phones, cameras, and all other electronics to be checked with security before entering their facilities. I've worked with companies that require photos for their own internal use be taken by a designated employee and cleared by a manager before they are released.
With all that said, it doesn't hurt to ask. I wouldn't expect somewhere like Intel to welcome you with open arms, but a small factory might let you in if you can make a compelling case to the owner or manager. Depending on local laws and employment contracts there could well be employee privacy concerns to deal with.
In Ontario there is an annual event where many office and historic buildings that are generally closed to the public allow tourists and photography:
City of Toronto: Doors Open Toronto - 150 buildings citywide open their doors 
Originally posted by jogiba 
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