My experience mirrors that of rwoman, albeit with AS. Whenever I book an AS flight through DL's website, I am always redirected away from DL's website at OLCI. Since I try to OLCI around 24hrs in advance (a habit ingrained from flying SW), a change in equipment or schedule made by AS would be made apparent to me the day before showing up at the airport ready to go.

That being said, I still agree that Delta's online reservation and customer notification system needs to be provisioned to handle this eventuality, so as to notify customers who booked flights through Delta of the same information that Delta later acquires about those flights, including whether or not they are cancelled altogether, to any extent that information is already known by Delta.

As for redress, I'm sure that Delta believes that they were already doing the OP a huge favor by "buying" a last minute accommodation booking on BA, for what Delta might believe is the OP's fault by not doing an OLCI the day prior. I'm not agreeing or disagreeing here, I'm just trying to look at the situation from Delta's possible point of view. They may believe they have already been as accommodating as warrantable in this situation. I would give Delta's potential point of view some consideration when making my case for more compensation for the inconvenience.