In OTRS 2.4.2 we are constantly getting escalation notifications.

This is the relevant entry in GenericAgent.pm:

%Jobs = (
        'send escalation notifications' => {
#               Escalation => 1,
                TicketEscalationTimeOlderMinutes => -60,
                Locks => ['unlock'],
                States => ['new', 'open'],

                # new ticket properties
                New => {
                        # Module => 'Kernel::System::GenericAgent::NotifyAgentGroupOfCustomQueue',
                        # notify all agents who have rw permissions on the ticket
                        Module => 'Kernel::System::GenericAgent::NotifyAgentGroupWithWritePermission',
                },
        },
);


As you can see, I'm using NotifyAgentGroupWithWritePermission.pm instead of NotifyAgentGroupOfCustomQueue.pm.

AFAIK this same configuration used to work with 2.3.4.