Just to be clear, the emails were the grounds, rather than the evidence, on which UEFA justified undertaking its investigation, which CAS felt was justified. There were other stories, including the Mancini contract, the Fordham image rights payments (which UEFA already knew about) and a few other things. Generally speaking, it requires a reasonable suspicion that rules or laws have been broken for an investigation and requesting evidence to take place, and the Der Spiegel articles provided that.
What they then did was ask us for the full email chains and any other pertinent documents. This is where the disputes over cooperation started, as our legal advisers resisted some of these requests, on the grounds that they weren't pertinent or relevant. In effect, it was a 'fishing expedition'. CAS actually questioned why UEFA didn't hold out for some emails they thought they were entitled to, and brought the charges before they had those.
We didn't provide some documents that we later supplied to CAS however. You'd have to wonder why we chose that course of actio and whether UEFA would have not gone ahead with the referral of the case to the Adjudicatory Chamber if we had provided those. We don't know the legal details though so it is pure speculation.
What we do know is that the AC found against us, and issued the 2-season ban, which was overturned by CAS, who did have all the evidence.
The PL likewise can only act based on a reasonable suspicion that we've broken rules and the emails gave them that. But unless we've given the PL's lawyers something that we didn't give to UEFA or CAS, then they're unlikely to be any more succesful than UEFA were.