This has been my experience with UL and CSA inspectors as well. They do have an agreement that one is supposed to accept the others mark. I have had extensive conversations with both. However, they both agree that the inspectors can lockout a UL panel if it doesn't have CSA (CSA inspector). It is now, purely a political issue. As far as obtaining a UL508 listing of panels, this can be costly since the appropriate agency has to monitor the manufacturing for a while, at your expense.
My problem with the whole UL issue is their prices are going through the roof as well as their turn around time. Yes, there is 3rd parties but they still require a UL review of their data so the turn around time is often the same. The third parties are not much cheaper either, since UL has to review it, they still have to be paid. CSA on the other hand, has good turn around times and prices. Unfortunately, that doesn't do much good in the US, but it should be equivalent. CSA, however, does not look at plastics, whereas UL does. This includes enclosures. I wanted to develop a product but would not get UL or CSA on it right away, due to cost, but would be able to put CE on it (can self certify with CE-do own testing, etc). How marketable is a product in the US and Canada without UL or CSA mark but with CE? Probably not very marketable because of inspectors. CE is even more stringent than UL or CSA.
Gordon, You say it has to be equivalent to CSA, what would be an equivalent? A UL stamp? Is the acceptance of the 'equivalent' a given or will it depend on the inspector that comes that day? Thanks to all