That is bad news. A 60% chance of making it back and a 4 to 6 month spell are highly optimistic opinions from my experience. At least it is only a fracture and that would be what the vet's are counting on. But 4 screws suggest it is a pretty long fracture.
I had a very honest trotter back in 2003/04 season which won a couple of horse of the year awards from a single preparation. Second up in the new season off 20 metres he was up running third by the fist turn when his near side hind pastern split in half. The bone resembles a Peter's Two in One ice cream (for those old enough to remember them) and separated right down the middle.
The choice was try and save him as a paddock horse or say goodbye. Some excellent veterinary work and a lot of money saved him. He had three screws inserted, the middle one from the opposing side of the bone. Four weeks boxed at the vet's in a fibreglass cast (which I have kept as a souvenir) followed by four weeks boxed at home with a constrictive bandage at home was needed. It was a successful procedure and the morning I let him run in the paddock my wife couldn't look.
About a year after the injury I had too load a mare to take to the vet's. The trotter followed her into the yard so I rang the vet and booked him in for x-rays. I did not tell him of the previous "salvage" prognosis, he was an extremely experienced and honest equine specialist.
He rang me the following day to say the pastern had healed extremely well but he was concerned he may have incurred an undiagnosed fracture to the fetlock. He told me he expected the horse may get back to trialling stage of a preparation but would be likely to go amiss when racing pressure was applied.
I was thrilled with his summary, far better than the original prognosis and he said the horse would be fine to ride. He has been with my neice used as a hack irregularly over the past 16 years, loving his life. He is 23 now and pretty arthritic in the injured leg and his eyesight isn't what was but we are all happy.
As smart as he was he was no Plymouth Chubb. Given that horse's ability and stakes banked I can understand his owners throwing the kitchen sink into their efforts to get him back on the track and I wholeheartedly wish them well.
However, as I have learned, time, time and then more time is the best chance with this type of injury. He is only three and would still be growing and maturing. I don't expect to see him at the races at least until midway through his 4 year old season. If at all. Fingers crossed I am wrong.