Becky you ought to be able to prune a brug as an espalier, but you'll have to let it reach away from the fence or wall a little bit because the huge flowers hang down or face sideways. If it was too near the wall they will be squished.
Brugs love to be pruned, especially if they are in containers. You could fasten it to the wall by the trunk then just prune the branches as needed after blooming.
