oh dear that is a shame but they may well resprout but they wont bear any decent fruit for a while. is your friend aware of what he has done? if not i would tell him so he doesnt do it again. that is if you are still friends.
an elderly neighbour had some door to door knockers who did the same to his bramley. 5 yrs later he has fruit again, more than enough for his needs. addmittedly the tree doesnt look particularly pretty but it is alive.
welcome to GoY.

That really is a shame! I'm so sorry to hear it. I know you must be upset - but Sbg is right. It will take a while, but I'm sure they'll recover. Try not to look at them!

They may recover, you will need to cultivate round each tree, also all cuts should be painted with Stockholm Tar or Ambrax. In late winter dress around each one with Blood, Fish and Bone followed by a dressing of Carbonate of Lime two weeks later. Apply plenty of water in the spring and summer.

We pruned our Apple trees with a chain saw two years ago, as they were outgrowing their allotted space. They produced fruit the following year and this, no trouble. However, I will say that I knew what I was doing.
Your Plum tree may be the major loswer in this. They should not be pruned after the beginning of September or there is a chance that they will get Silverleaf. This is a fungus which is active from early Autumn onwards. It gets in through pruning wounds, so as suggested, get them painted with wound paint a.s.a.p.

Cuts SHOULDN'T be painted as your more likely to seal IN disease etc. Leave them to nnaturally heal, just like they would do anyway..
They will all need re trainign to build up the fruiting spurs ince growth begins over the next fwew years and i agree with Owdboggy about the plum Silver leaf.

The conflict between what Docbob says and what Nicky says is simply a change in thinking - years ago, we were all told to paint cuts with Arbrex or similar on trees in particular - now the thinking is that they're better without. I dunno, it's hard to keep up sometimes...

If you like Owdboggy having pruned and trained all sorts of fruit trees, you will have used the old with the new. I have cauterized large cuts with red hot irons, the main reason being that now sap flow does not slow down with mild winters and in Spain this will be the main reason for the trees dying. Also disease will grow in the bleeding sap. As again OB has talked about silver leaf, scab will affect the apple, canker will appear. Sealing the wounds will keep out more than is sealed in.

surley the thing to do is paint them the moment you cut them just like a humans cut.like first aid.if theyve been cut for a while id be inclined to agree with nicky08 .sorry doc hope your well

Well Leigh, it sounds like the damage has only just been done, so early attention is important to save the trees.

i agree or nicky will be i right i think.hope your well mate take care

I like the way you keep changing your Avatar Leigh, are you trying to confuse us? (easily done).

thank you all for replying so speedily- I think he knows because he saw my face drain of blood! I agree that they look neater- like a professional orchard I suppose, but have lost their grace.Anyway I shall mention my new found knowledge.he did actually say well you had too many plums to cope with???? but they were gorgeous big round yellow ones- probably turn out like footballs now...apples not fruiting at all aprt from a couple of grotty ones- flavour lovely though so here´s hoping.

on sealing- some of the lower branches do have dark cores and a bit hollow in others- is this because they were just old or is that disease and will sealing help or hinder?

no doc a change is as good as a rest and more interesting.thats a bird box fo sparrows as well as theatrical masks.if it does confuse then i wont change it sorry.

if there very new cuts seal them whitefrizz if not it mite be to late

Done about 14 days ago.

No Leigh, I was joking, really enjoy your Avatars. Please don't stop.

ok doc lol as for white 14 days is 14 days of germs,desease getting in but it mite still be worth it doc knows better than me realy

Arbrax has a fungicide in it. All the black cuts and those with holes in should be cut back to healthy growth. Any holes in the trunk should be filled with concrete.

nice one doc glad i know that but i guess i already did.if you dont get a nasty wound to the doctors they have to cut it back to healthy skin.same thing realy i guess