As long as they have enough room in the tub (and areas to bask/warm, etc.), I think it can easily be done. George Van Horn actually had several Columbian and Brazilian (maybe more subspecies in there too) rainbow boas in the same enclosure last time I was at the St. Cloud Serpentarium. I even saw two pairs copulating. (I also recall reading of breeding success with other members of Epicrates when put in groups like that.)
That said, I wouldn't do it myself, nor would I really recommend it to you. I'm just stating that I've seen it done before by a well-respected individual with no apparent problems. Just the idea of there being a slight possibility of something happening is enough to deter me from it.