If it's a delta wound motor then current will be zero.
If it's a wye-wound three-phase motor then no current will flow unless you hook up a ground to the neutral.
That part was probably an obvious unstated assumption.
Definitely won't start rotate (although if you started it rotating with external force it might concievably stay rotating similar to single-phase motor).
I believe it's possible that it might draw slightly lower current than a locked rotor current.
The flux path is much different. In normal 3-phase we have flux from one pole group a,b',c acting together with max mmf equal to 1.5 times that of a single pole-phase group(i.e. a) and returning through adjacent pole phase groups a',b,c' on either side.
In single phase configuration, the max flux is smaller (1 times instead of 1.5 times) but the turns per phase remain the same.
Also the flux path length within iron is much shorter (a returns through adjacent pole-phase groups b' and c' which is 1/3 the normal circumferential length of the flux path) but air gap length remains the same.
Both of the above would likely have an effect on the inductances associated with equivalent circuit parameters Xm, X1, X2.
Also the stator now acts as if it had 3 times as many poles as before. Rotor frequency is three times higher. I believe this factor would increase X2 and possibly R2 for large motors (where skin effect is an important factor in rotor resistance).
Altogether it's a mixed bag of effects. I'm not sure which will predominate. Since in a normal motor the series reactances X1 and X2 are the primary factors determinng
LRA ~ V/(X1 +X2), it seems reasonable that the increase in X2 due to increased rotor frequency might be the most dominant effect, resulting in somewhat lower current than LRC.
Just a guess. Any more thoughts?
