Ok, I understand the basic problem - i.e. that game uses same depth for both the reception and transmission.
However, opposite what you told about Foxtrot/688 example, CrazyIvan, I'm able to see friendly subs through link even if they are a lot deeper than comms depth. I don't know why, but that's the case. I have also checked my settings - everything is ok (I mean no "show truth" set or something else - only "show link contacts" is checked). Maybe this is releated to the original problem with reception/transmitting depths.