Let δA, δB, δC be the circumcircles of △AA1A2, △BB1B2, △CC1C2. The general strategy of the solution is to find two different points having equal power with respect to δA, δB, δC.
Claim. A1 is the circumcentre of A2BC and cyclic variations.
Proof. Since A1 lies on the perpendicular bisector of BC and inside △BA2C, it suffices to prove ∠BA1C=2∠BA2C. This follows from
∠BA2C=∠A2BA+∠BAC+∠ACA2=21((180∘−∠AC1B)+(180∘−∠CB1A))+60∘=240∘−21(480∘−∠BA1C)=21∠BA1C
□

The circumcentres above give
∠B1B2C1=∠B1B2A=∠B2AB1=∠C1AC2=∠AC2C1=∠B1C2C1
and so B1C1B2C2 is cyclic. Likewise C1A1C2A2 and A1B1A2B2 are cyclic. Note that hexagon A1B2C1A2B1C2 is not cyclic since
∠C2A1B2+∠B2C1A2+∠A2B1C2=480∘=360∘.
Thus we can apply radical axis theorem to the three circles to show that A1A2, B1B2, C1C2 concur at a point X and this point has equal power with respect to δA, δB, δC.
Let the circumcircle of △A2BC meet δA at A3=A2. Define B3 and C3 similarly.
Claim. BCB3C3 cyclic.
Proof. Using directed angles
⋠BC3C=∡BC3C2+C2C3C=∡BAC2+C2C1C=90∘+∤(C1C,AC2)+C2C1C=90∘+∤C1C2B1.(1)
Similarly ⋡CB3B=90∘+∡B1B2C1. Hence, using B1C1B2C2 cyclic
BB 3C = 90 + C 1B 2B 1 = 90 + C 1C 2B 1 = BC 3C
as required. □

Similarly CAC3A3 and ABA3B3 are cyclic. AC3BA3CB3 is not cyclic because then AB2CB3 cyclic would mean B2 lies on ⊙ABC which is impossible since B2 lies inside △ABC. Thus we can apply radical axis theorem to the three circles to get AA3, BB3, CC3 concur at a point Y which has equal power with respect to δA, δB, δC.
We now make some technical observations before finishing.
- Let O be the centre of △ABC. We have that
∠BA1C=480∘−∠CB1A−∠AC1B>480∘−180∘−180∘=120∘.
so A1 lies inside △BOC. We have similar results for B1, C1 and thus △BA1C, △CB1A, △AC1B have disjoint interiors. It follows that A1B2C1A2B1C2 is a convex hexagon thus X lies on segment A1A2 and therefore is inside δA.
- Since A1 is the centre of A2BC we have that A1A2=A1A3 so, from cyclic quadrilateral AA2A1A3 we get that lines AA2 and AA3≡AY are reflections in line AA1. As X lies on segment A1A2, the only way X≡Y is if A1 and A2 both lie on the perpendicular bisector of BC. But this forces B1 and C1 to also be reflections in this line meaning A1B1=A1C1 contradicting the scalene condition.
Summarising, we have distinct points X,Y with equal power with respect to δA, δB, δC thus these circles have a common radical axis. As X lies inside δA (and similarly δB, δC), this radical axis intersects the circles at two points and so δA, δB, δC have two points in common.