Can we order DO to refresh the content of an objects? I.e. reread the data from the DB.

Yes:

var originalMergeMode = disconnectedState.MergeMode; // MergeMode.Strict by default
disconnectedState.MergeMode = MergeMode.PreferNew;
try {
  // Read some data. It will replace the data in DS in any case.
}
finally {
  disconnectedState.MergeMode = originalMergeMode;
}

MergeMode defines default merge policy for DisconnectedState.

Does DO allow for changes in the DB to be taken into memory when no local changes have been made?

No. I.e. currently you can:

1. replace know Entity state with the new one
2. reject new ones, if there is a known Entity state
3. throw an exception in case there is known + new Entity with conflicting version. Note that "known version" is the version of Entity on the moment it was read for the first time (i.e. not the current one).

In your case we must add a flag like MergeMode.UpdateUnchanged - is it a good solution?