While my experience was with a volunteer effort and not related to my job, I took photos for a conference for them, and then for some reason was shut out from communications (they had a change in leadership and I was viewed as 'from the previous group'). I didn't deliver the photos as it all fell apart but months later was 'threatened' if I didn't provide the photos.

While slightly different, since there wasn't any real delivery contract as to what or how many photos I was to deliver, to just diffuse and end it, I sent low size, low res jpg shots of the lowest coverage of the conference (I took 600 photos over 2 days of a conference, delivered 20).

I fulfilled the request to provide them photos, while feeling good that they wouldn't be able to use a 640X480 highly compressed photos. Whenever they pushed for photos, I could say that I did deliver photos, sorry they weren't what you wanted but you never stipulated that part.......

They may "own" the photos or not based on whatever work for hire, or at-will condition may or may not existed, but instead of fighting, or pushing luck to cause issue (erasing the card), just deliver low res version and you can say you did this for quick turn around in camera. Since you are no longer employed by them, you won't have the battle to edit them.......and if there is a push to a shove, you did what was asked - deliver photos of the day.