[SalesForce] When are workflow email alerts sent in a transaction’s order of execution

Yes, the root of this is that cross object formula fields can't be of type email and email alerts on your child object can't reference email fields on parent objects unless parent is a Contact)

Option 1

If Issue__c is a detail object in a master-detail relationship, then when Issue__c.status = 'Solved', use a workflow to set a field update on Office__c, say, has_resolved_issue__c, a boolean.

Then, a subsequent workflow can fire the email alert to the current point person on the Office and clear via field update the has_resolved_issue__c to false. You may need to copy more fields from the solved issue to the Office to make available to the email template -- or, if using a VF email template, that template, can through a component controller, access the Office's child Issues.

Option 2

As you suggested, a trigger on Office__c that when point person changes, propagates that point person email down into all child Issue objects.

// after update trigger -- this is untested
Set<ID> officeIdSyncSet = new Set<ID> ();
for (Office__c of : Trigger.new)
  if (of.status__c != Trigger.oldMap.get(of.id).status__c)
     officeIdSyncSet.add(of.id);

List<Issue__c> issUpdList = new List<Issues__c> ();
for (Office__c of : [select id, point_of_contact__c,  // fetch children issues
                      (select id, point_of_contact__c
                         from Issues__r where status != 'Solved')
                      from Office__c where id in : officeIdSyncSet] )
   for (Issue__c is : of.issues__r) {
       is.point_of_contact__c = of.point_of_contact__c;  // sync POC from parent
       issUpdList.add(is);
   }

 update issUpdList;  // does the sync via DML

Preamble (altered to reflect comment trail)

With a rule NOT( ISNULL( Maintenance__c ) ) and workflow evaluation criteria of:

Evaluation Criteria :  created, and any time it’s edited to subsequently meet criteria

The workflow rule only executes if the value of the field changes from null to nonNull or when the record is created.

The workflow will not evaluate at all if the Maintenance__c changes from one non-null value to another non-null value as that won't "subsequently meet criteria" (true is still true). Note, for time-based workflows, the Every time it is edited evaluation radio button is not available.

Once the time-based workflow is entered for the object, the object stays in that workflow until the time-based condition is no longer true (maintenance start date becomes null) or the time trigger finally happens (345 days after account.maintenance_start_date__c). If the maintenance start date is changed on the Account, the time based trigger adjusts accordingly per the doc:

What happens if I update the value of a date field used in a time trigger? If you update the date field used in a time trigger, Salesforce recalculates the time trigger as long as the time trigger has not yet fired and the recalculation does not reschedule the time trigger to a date in the past.

For example, if a workflow rule alerts the opportunity owner seven days before the opportunity close date and the close date is set to 2/20/2008, Salesforce sends the alert on 2/13/2008. If you update the close date to 2/10/2008 and the current date is 2/2/2008 or before, Salesforce reschedules the alert for 2/3/2008. The evaluation date of pending actions is ALWAYS reevaluated and updated if necessary irrespective of the rule criteria. Of course, if the rule is evaluated to false, it does not matter as the actions are removed from the queue.

If you were backdating to a date in the past, per the doc, the time trigger does not adjust