Kashrut standards

Question

In a recent interview, an expert in food technology stated as follows, when asked if a company not under kosher supervision would keep the same oil between pork rinds and french fries: " "Yes…a non-kosher company, I can guarantee you…it all boils down to economics." If this is the case, and since the expert says it is (and he is not Jewish and has no connection to the kashrut industry" does that mean that there is a problem buying foods without hashgachah that have been cooked in oil? If not, why not? Do you apply the logic of setam kelim einam benei yomam to assume that the vegetable oil a certain product was made in is not the same oil used for a non-kosher product?