Goosegg,
You, and the article you reference, make points with which I agree in terms of the challenges of a Milb player to both know and to enforce his rights under the Workers' Compensation laws when they are injured and especially when the injury results in need for extensive treatment, second opinions, surgery and permanent disability.
On the other hand, AB1309, the law passed in CA which became effective in September of 2013, does not impact the rights of a CA resident or a player who spends most of their championship seasons assigned to a CA team or playing in CA. Each can pursue claims for medical treatment and disability benefits under the CA. Workers' Compensation laws.
What AB1309 was designed to do was prevent professional athletes who played in Buffalo, NY, for instance, from pursuing a WC claim in CA. because they played one or two games in their career in CA.
Whether and how the new law and the new amendments to the MILB contract will impact any player from out of State who is permanently disabled with need for medical while playing a full championship season in the California league is probably an open question to be assessed in terms of other laws in our State.