I can't say as I know for sure but this is probably true. It should be true anyway. But whether he sent information directly to OSN (however one would do that) or to a casino who then reported to OSN. That information came from him.
Additionally Mdawg claims he is friendly with some of the pit folks in the high limit room. they pat him on the back. He could have gone directly through them. And the Casino he stayed at mostly and played at mostly at that time, Cosmo, just happens to be one of the bigger database contributors in Las Vegas.
How he did it is less important than that he did this. It is not in question. He knows it. I know it. I think anyone with an ounce of objectivity knows it.