In trade negotiations? I seriously doubt it. Even if it were technically "tampering" as defined by the CBA, it's probably not good business to file a tampering complaint against a team you're trying to negotiate a trade with.
My point isn't about what BB and Yee should do to maximize a trade value. It's that LaCanfora is acting as if this permission has already been granted. And you're assuming that the team wants to actively trade him, and has granted that permission.
Whether permission was granted or not was unknown, so he's either breaking news here, or he has overlooked a pretty basic step in the process. I want to know which one it is.
Because if the team is honest about not wanting to trade Jimmy, then tampering could matter. For example, if BB's plan is to franchise him, that would guarantee him around $25M for a season, and Jimmy G/Yee probably figure they're holding him to trade him like Cassel. They might sign the deal right away so it can't be rescinded later. Or they might play hardball and not sign it to try to exert some leverage on where they get traded to.
But if Yee has been negotiating in the background and finds out a team will give Jimmy G a deal like Brock Osweiler (stupid, but hey, it happens), that changes the nature of that negotiation considerably. If it's $25M guaranteed vs. playing hardball and then potentially watching the starting jobs and free agency money dry up as you wait, compared to knowing you already have a better deal in hand before free agency even starts.
Of course that's tampering. Even if you are planning on trading him, teams can't tamper to destroy leverage in negotiations, and agents can't work with other teams to try to acquire a guy whose team hasn't given them that permission.
So I'd be very curious if LaCanfora has inside info here, or if this was just something he lazily overlooked.