We have a BrowserStack subscription. We have limited seats (5 at the time of this writing) and can purchase more as necessary, but would like to aim to spread them through the engineering organization as evenly as possible under the assumption that each team may have only a few people at most who will need to be doing cross-browser testing anyway. It gets expensive pretty fast.
David Joy (Deactivated) is the administrator of the account. Get in touch if you'd like to claim a seat.