I'm a #1 fan of good ol' jb and recomend it for all types of repairs. In this case, however, I leave jb on the shelf and would use model glue. Jb just pukeys the plastic together. Model glue melts the plastic, thus fuses it.

Clamping tip for hard to hold together peices: Run the line of glue and leave an area in the break free of model glue, and use a a dab of crazy glue or hot glue in that area to act as a tack while the glue dries.