In general, identifying baits and preys, and thus reciprocality, from the bioplex data.frames obtained via getBioPlex alone is not straightforward as there is some collapsing involved in generating these files.
Files containing the uncollapsed / directed bait-prey interactions are now available on the BioPlex homepage.
Functions such as getBioPlex would then get a boolean argument collapsed = TRUE/FALSE that would allow a user to indicate whether s/he would like to obtain interactions in collapsed form or not.