Can this sp2 lone pair resonate? In methyl isocyanate, $\ce{CH3CNO}$, shown below,


 it seems that the nitrogen lone pair can resonate with the carbon oxygen double bond, generating a resonance structure something like acetonitrile oxide:



In that case, why is the geometry around the nitrogen in the methyl isocyanate compound bent and not linear? Can the lone pair even resonate like that?

I remember in Klein's organic chemistry, it is stated that 


  Whenever an atom possesses both a π bond and a lone pair, they will not both participate in resonance


In methyl isocyanate, $\ce{CH3CNO}$, shown above, it seems that the nitrogen atom has both a π bond and a lone pair. So perhaps the sp2 lone pair on nitrogen atom cannot resonate with the carbon oxygen double bond? I am not sure.
Whenever an atom possesses both a π bond and a lone pair, they will not both participate in resonance


The sentence means that only one, either the  bond or the lone pair will participate in resonance if the atom has both.



For example, in a pyridine, the nitrogen has a lone pair and it is also attached to a  bond.

Here, however, only the  bond participates in resonance because it is in the plane perpendicular to the molecule, while the lone pair is not.





Methyl isocyanate is best represented by a group of three resonance structures:



Here is the 3D structure of the most significant resonance structure of methyl isocyanate: