I have no competencies but I'd certainly strongly recommend the techs be required to take an official IV certification class, demonstrate the requisite number of "practice sticks," and as part of the yearly competency (at first, at least), document X number of IVs started yearly (Chief Tech or RN or Radiologists determine what number is acceptable). The last part may be discontinued if it turns out the techs are ALL starting many IVs per day, and thus maintain their skills.
What happens in case of a reaction? Do the techs know what to watch for ("reaction resembling allergy," cf true "allergy?") and how to respond, based on the presentation and progression of the s/sx? Is the Radiologist in the room or just around the corner, in case of a reaction? Who will push meds and observe the pts with mild/moderate reactions afterwards? What printed instructions will the pts receive post-reaction and who will document the reaction in the pt chart? The techs should all have a yearly inservice on Contrast administration, as it's not just allergic reactions that are the danger here, it's the potential renal problems, problems with pts on Metformin (when was the last dose?), brittle diabetics who've been NPO for the CT, and whose sugar may bottom out while waiting (delays do happen!), etc etc.
All the techs BLS-trained? Do they know how to administer O2 and set up/use suction? How to put on a BP cuff and take VS? Just as important: WHEN to take VS?
PM me if you like. As you can tell, it's hard for me to give a succinct answer without more info.