I don't know if this is obvious to you or not, but if ANYONE calls at ANY time and it's inconvenient for ANY reason, you can say "I can't talk right now; I'll call you back, ok?"
BOTH of your men need to just grow up and deal with that. That is how it WORKS with the phone. This business with micro-managing "This is B's time, this is J's time" is fine when it comes to things like over-nights or plans that would require you to be in two different places at once, but since you're talking about "Losing battles" so you can "win the war", consider also CHOOSING your battles. Is this mincy stuff about the phone really so devastating that everyone has to agree to a PLAN about it? If it is a "war" you plan to WIN (and I understand that you're using the "battle/war" analogy as a euphemism for "short-term/long-term"), then everyone is going to have to learn to deal with mundane, every-day things such as brushing teeth, taking out the trash, and answering the telephone. You wouldn't agonize over "rules" about brushing your teeth around either of these men, so why not try using that comparison as a tool to establish a neutral, non-threatening mindset around answering the phone and saying "Sorry, can't talk now. I'll call you back."
GAUD! I'm reading what I write and I cannot BELIEVE that GROWN MEN (and women, too) need these things POINTED OUT to them!!! I have to end this post because my cynicism and sarcasm is boiling up inside of me and about to spew out all over my keyboard.