Section 1.A defines who the bargaining agent is. it's unambiguous. What is a little ambiguous is the way the NMB views company actions during an organizing drive, or an election. Delta has earned re-voting for their actions during union elections. But this is not a union election. it's an organizing drive.
Section 24.P grants ALPA specific access. Past practice is a blurry concept in labor law, since even the NMB has reversed itself at least twice in the past few years on the voting requirements. Delta must comply with the RLA and LMDRA, which recognize the authorized bargaining agent's status. DPA has no special status under RLA or LMDRA, so Delta doesn't have to give them access. The interim president of the DPA has written a complaint letter about being kicked out of the DTW pilot lounge area. It's a complaint, not an injunction.
newK listed a few cases that matter for factory workers. They are not applicable to us. We aren't governed by the NLRB. We fall under the NMB because we are governed by the RLA. We have special tax provisions, work rules (duty time), medical standards, and union rules (eg - contracts that never "expire").