The companies that are hush-hush about their rates are that way because of this. It's frequently because their rates are dreadful, if not completely backwards/fraudulent (i.e. negative swap on carry longs, watch Dukascopy and MBT/EFX since the chief perpetrators).
A firm's swap rates must be clearly recorded on their website, and it is a pity so few have adhered to ethics of
http://individuals.interactivebroker...?ib_entity=llc and
https://fx2.oanda.com/user/interee.html inside this section (both of whom possess the most reasonable rates in the entire retail world).