Sorry you have not had an answer earlier, we tend to forget the pets section is here and use animals and nature more.
They need to do this when they are not just going to work i.e. make a special effort to take the dog out another time when they have time to train it.
Every time the dog barks they need to stop and either put the dog in the sit or the down if it knows what this means or else turn and go back where they came from (hence the time needed to do it). If they let the pup get away with it because they have no time to spend then it will just get worse.
Use a titbit and reward the dog if it sits or stops barking.
Try taking a toy with them and get the dogs attention on it by holding it just above the dogs head when walking.
Do several little stints where you walk for a few yards then turn and go back the other way. Just keep changing direction and rewarding the puppy who should be paying attention by now wondering what the hell they are playing at!).
What sort of a collar have they got on it? A half check or combi collar will allow them to give the pup a slight tug on the neck without hurting it, and the resulting release of the collar when the pup is behaving will reward the dog for paying attention.
Get them to take the pup to obedience classes where he will learn to walk properly and how to intereact with other dogs/people.
If al else fails, give him to the person who he so obviously wants to get to!