Get Deliery WorkItem using baseline UUID

The short answer is "no". Baselines and snapshots are not associated to work items in any way. You can think of baselines as a pointer (or even a 'tag') which points to a particular spot in the history of a component configuration (or a different way to think of it is a pointer to the tip of an ordered list of change sets, in the order that the change sets were created/added in that configuration). A snapshot is just a collection of baselines. Change sets are associated with a work item, but not baselines or snapshots. So it is possible to enumerate 'every' change set in that baseline, and collect up all the associated work items (however the list of change sets / work items is likely A LOT), so I'm not sure this is what you want to do.