i would follow the same planting dates for fall broccoli, transplants around July. brussels are extreme long season and when planted a couple of weeks before frost in spring, expect to start harvest after first frost in the fall. we just dont have the long cool season that brussels need to be grown successfully. they can take frost hits well but will be killed by hard freezes, but you can mulch up to the top of the plant for a winter harvest. they will almost stop growing in summer until cool weather comes back in the fall. the bad thing about a midsummer planting is that the young plants will sometimes bolt and flower when cool fall weather hits. they require WELL drained soil and not too much nitrogen, a feeding of of triple 10 or triple 13 a time or two throughout the growing season is all that they require.
good luck and if you try it let us know how they turn out. ive grown brocolli in the spring and about the only way ive found to grow successfully is to start seeds in December-January for transplants in February-March. but you have to have your beds ready in the fall and straw mulched so that all is needed is to pull back the straw and plant the transplants. brussels should be no different.