I agree - just call the hotel.
There seem to be basically two types of deals.
Hotels (usually located very close to major airports) may give generic "crew rates" for crewmembers who are traveling for duty such as commuters. They may ask to see a valid ID but they won't discriminate based upon which airline you fly for.
Some other hotels (often located farther away from the airport) that have contracts with a particular airline MAY extend a special rate to crewmembers who are traveling for pleasure. These hotels MAY only give that room rate to the employees of the airlines they currently have contracts with for on-duty rooms. Usually, these discounts are not termed the "crew rate" by the hotel staff but instead use the "_____ Airlines Rate". A hotel might have a more favorable deal for one airline over another in this case, so the deal they offered would depend on your employer.