McLaren Mercedes have copied the snowplough that featured on the 2009 Williams contender. As McLaren introduced it as of its first test with the MP4/25, Williams dumped it in favour of cleaner frontal aerodynamic.
The system itself is fairly simple in its operation and effectively acts like a diffuser mounted higher above the ground. Part of the airflow under the nose is split left and right of the plough, while everything that flows underneath is slightly expanded, reducing its pressure and therefore creating a suction effect of the car towards the ground. The aerodynamics of it are also similar to the nosecone of the Renault R29, but possibly a bit more efficient.