One thing is a lost pump and quite another thing is a lost hydraulic system.
If a system is lost, it is lost, no matter how many pumps you have. Actually, you have to switch them all, including the PTU if any. isolating the system and thus preventing it from creating more problems, means that we lose the system.
If only the y eng pump is lost we can use the Y elec, if we were so unlucky that we lost the PTU, too. otherwise it is better to let the PTU do its job.