While the above mentioned reasons do have some merit, there is another, more practical reason behind the "intrusion" of other DCI carriers into ASA's "domain."
Delta/ASA/DCI are committed to as large a jet fleet as possible and serving as many destinations with all jet service as feasible. As such, ASA's Brasilia (EMB-120) fleet is slowly (or actually, quite quickly) being retired. These former (and soon to be former) E120 routes (ABY, FAY, BQK, CRW, EVV, etc) are being covered by new jets - jets that normally would be used for expansion to new destinations. Until the E120 fleet is reduced to the level desired, you will continue to see some new jets being used to replace the props rather than service new cities. At that time, the new jets will be used instead for expansion. Until that time, we will see other DCI carriers (Comair, Skywest and maybe one day ACA) being used to suppliment ASA service in ATL to "new" destinations.
Well, then why is ACA moving in on Comair in CVG? Well, the vast majority of cities ACA is servicing from CVG also have ACA service to JFK, LGA, and BOS. Since ACA already serves these cities from "their" northern hubs and some trips into CVG do not require 50 seats (ie Comair's CRJs), DCI is using ACA to suppliment Comair so that Comair can in turn suppliment ASA in ATL and DFW.
Skywest's DFW expansion is simple. United Express, Inc. reduced their orders for Skywest CRJ service on the west coast and as a result, Skywest had a surplus of planes, pilots and flight attendants. Delta needs the attentional support in their DFW hub (for both replacing ASA props AND unprofitable Delta mainline routes) and requested Skywest to expand in DFW - Skywest was smart and accepted.
While many pilots would like to think that Delta brass want to screw them over as much as possible, this is not hardly the case. Mullin and his cohorts LOVE DCI and their regional jets, but are going to use the various bodies effectively. Strike protection is a cause for concern, but does NOT dictate operations. Simple economics, company capacity and other more placid variables determine proportionment and use of assets.
In any case, I wish my co-workers at ASA the best of luck in their forthcoming negociations, but I would also pray that they keep calm, civil heads and be more realistic in their assumptions. This isn't war - it's business.
Ignorantia juris neminem excusat.