I dont know if any of that is real or not, but I heard that Maxwell did admit to calling in to WMMS at various times.
The funny thing about all this is that while maybe some fans of the shows think there is a rivalry, and we know that Maxwell and his crew think there is a rivalry. They are losing thier shirts and Cox is thriving in his old spot, so thats natural. But Cox himself, at least on the air, doesnt seem to care either way about him or his show. He doenst compete with him, they are on at different times. Cox wasnt even in town when he was on the air at WMMS, so he really hasnt heard him or his show from then. According to Cox, there is no rivalry. Maxwell does his thing and Cox does his. But here, Maxwell and his fans (whats left of them) are waging war and even some Cox fans are engaging in the warfare. Meanwhile, Cox couldnt care less, he is just doing his thing, and doesnt really care what he or his fans really do.