Note on 2D Schr\"odinger operators with delta-interactions on angles and crossing lines

In this note we sharpen the lower bound from [LLP10] on the spectrum of the 2D Schroedinger operator with a delta-interaction supported on a planar angle. Using the same method we obtain the lower bound on the spectrum of the 2D Schroedinger operator with a delta-interaction supported on crossing straight lines. The latter operators arise in the three-body quantum problem with delta-interactions between particles.