Which foods are most likely contaminated by dairy due to processing methods used?
Practices will differ with country (or community in some cases) of origin. A country where few dairy products are commonly consumed or produced, or where a significant amount of the population is not dairy tolerant (parts of asia) or where religious codex exists about dairy use (eg jewish communities) is likely to have different practices from scandinavian countries that lead the world in per-capita dairy consumption.

Equally, the country where the product is marketed/consumed is important, especially when it comes to what has to be declared on the label, with which tolerance levels, by whom. Also try to take advantage of multi-language, multi-market label text - sometimes important hints are found only in foreign language versions of ingredient lists or allergy advice (ever noticed that they sometimes differ - where it is unlikely that two different products are described)....