C# Parallel Task Library: Can I rely on task.ContinueWith() continuation to always be called?

Question

I create a Task which calls a method on a DI resolved service instance:

   using(var scope = container.BeginLifetimeScope())
   {
       var serviceInstance = scope.Resolve<IService>(serviceType);

       return Task.Factory.StartNew(serviceInstance.DoTheWork());
   }

Of course this is no good: as soon as the using-block is left, all the created dependencies living on the scope are disposed of - the call to "DoTheWork()" is not yet finished and still using the injected resources.

This is not what I want. My solution for now would be this:

   var scope = container.BeginLifetimeScope();
   var serviceInstance = scope.Resolve<IService>(serviceType);

   var task = Task.Factory.StartNew(serviceInstance.DoTheWork());

   task.ContinueWith(t => { scope.Dispose(); });

The question is: Is this safe or are there cases where the continuation is simply not called for whatever reason?