So, page 47 says (any attack). Notice smaller case 'a'. Now, there is an explicit Attack action that goes with Firearms, Close Combat, Athletics (Archery), and Exotics. There is also the explicit Cast a Spell action.
For me, given it is small 'a' attack and not big 'A' attack action, and one would rationally say that combat spells are an attack, that Called Shot could be used with targeted combat spells (i.e. Indirect Combat spells).
Any other thoughts, feedback, or explicit places in the rules that support or say otherwise.