Page 20 of Campaign Operations:
Combat personnel pulling double duty as technical personnel act as an astech if they have an appropriate Technician subskill (see p. 157, AToW) of 3 or higher, or a full tech if they have an appropriate Technician subskill of 6 or higher.
Does this mean all Tech Teams led by combatant personnel are Elite by definition? The Technician skill starts at a TN of 9 (AToW, page 142), and six levels will get it down to 3. Elite teams as defined by StratOps page 168 have base TNs of 5. Similarly, the AsTech requirement appears to drive Tech Teams supported by combatant AsTechs to the Veteran level (TN 9 less 3 levels yields TN 6, which is Veteran per StratOps page 168).
Also, the minimum skill levels listed for combatant personnel are the only minimum skill levels I see. Are personnel who are "just" Techs or AsTechs required to have skills at some level? Going by StratOps page 168 and AToW page 142, Green Techs would seem to have 0 skill, Regulars 2, Veterans 3, and Elites 4, but I have no idea what that could mean for AsTechs (though I'll note that per the CampOps requirement, it appears 3 skill levels is both "semi-skilled" (per text to the left of the table on page 168) and Veteran per the table).