Yes they can.
1. They may have gotten their numbers from Countrywide on different days or even a different hour on the same day. That is the most common reason for rates or fees to differ.
2. They may be quoting different programs such as one might be quoting full documentation (better rate and fees) the other might be quoting lighter documentation.
3. Someone may have gotten it wrong, or purposely jumped the gun. . Lets say the loan was $450,000, One broker might accidentally or intentionally (but incorrectly for the moment ) quote a conforming loan rate and another correctly quote a Jumbo rate.

However with loan limits set to change very soon, the loan may fall within the conventional rate structure soon anyway. The broker quoting the Jumbo rate will seem higher because he is conservative and not willing to quote something that has not been signed by the president yet, nor implemented by the GSE's. The broker quoting a conventional rate, may be willing to take the risk of quoting you a rate for a program that your loan size will probably conform to in 45 to 60 days, even if the ink is not dry yet.

4. Finally it is possible that the brokers have their own fees that do not match up with each other. Or someone calculated something differently, or some one made a mistake for the good, or someone else was being conservative (higher) with their estimate. Or that one made an improbably low estimate to get your business.

5. Picking the lowest quote, does not guarantee that you will get what they quote. nor does it mean you are any more likely to get a better deal from the lower quote. A quote is just an offer to do business.

6. A written good faith estimate gives you a little more to go on, since it is writing., but is still only an estimate, and is not binding on the broker or the lender.

7. The closest you can come to knowing what your rate and fees will be is when you lock in the loan rate.
( IN WRITING )
Yet locking in the loan rate more than 30 to 45 days away from the expected close of escrow can be much more expensive than allowing your rate to float, especially when interest rates are falling.

The best broker to go with is the one who can explain all of this to you. one that seems to know what they are doing, one that asks you a lot of questions. A really good broker may even discuss loan programs that you did not think of that might save you more money than the one you asked for.