private IEnumerable<DisconnectedPollingFanOutJobEntry> HostsAndGuestsView
        {
            get
            {
                return Hosts
                    .Select(e => e as DisconnectedPollingFanOutJobEntry)
                    //because we are dotnet 3.5 we can't use covariances
                    .Concat(Guests.Select(e => e as DisconnectedPollingFanOutJobEntry));
                    //so this as good as it gets.
            }
        }

and then i'd use it like

while (!CancelQueue &&
                   HostsAndGuestsView.Any(
                       e =>
                       e.DisconnectedJobState == DisconnectedPollingFanoutJobState.Pending ||
                       e.DisconnectedJobState == DisconnectedPollingFanoutJobState.Running)
                )