Repro steps:
1) Open my attached project and the only scene in it
2) Select both Particle Systems so you would see both simulations
3) Notice that particles from one of the systems collide with the Terrain
4) Notice that both systems are identical and should collide only with Default layer, whereas Plain and Terrain are on a different layer(NoCollision)

Expected behaviour - particles should not collide with Terrain

Reproduced in: 5.4.0b2; 5.3.1p3; 5.3.0f4
Not reproduced in: 5.2.3p3
Regression introduced in: 5.3