In article , "Lobster"
says...
I've just ended up pulling down all the laths and plaster off my old
bathroom wall - plaster was blown and removing the tiles from the
plaster was a non-starter. Now the wall on the opposite side of the
stud partition, which faces on to the landing is also in a pretty bad
state, blown in a lot of places. With the back of the wall now exposed
you can see all the nibs of plaster extruded through the laths have
broken off.

So before I put the plasterboard up in the bathroom I thought I might
have a stab at some remedial work. Ideally the landing wall wants to
come down too, but that ain't gonna happen any time soon! I thought I'd
try chucking 1:4 PVA all over the back, and then essentially applying a
very rough coat of Carlite bonding plaster to the back of the laths with
a view to it holding the blown plaster. All that will be concealed as
soon as the bathroom wall goes up.

It's got to be worth a go; has anyone tried this or got any refinements
to suggest (eg which type of plaster)?

You might get away with just lagging it with PVA (so it runs between
the lath and the plaster) then applying pressure from the other side
(with boards and props as others have suggested) until it's
thoroughly dry.