This is the best way I've found to cut holes into old plaster with wood laths. I use a cut out tool with a grout/tile bit for the plaster. I than switch to a wood/drywall bit to cut the wood laths. It makes for a clean hole without damage to the ceiling or wall.

Music provided by Argofox:
Hexalyte – Horizon
   • Hexalyte - Horizon [Argofox Release]