The comment that March 2013
The comment that March 2013 is the first month when all electric vehicle sales outpaced plug-in hybrids is not strictly true.
From April - Sept 2011 BEV sales outpaced PHEV's thanks to higher LEAF vs Volt Sales
This occurred again in Jan 2012 thanks to higher LEAF sales again.
As reported here March 2013 saw a repeat performance.
What is different about March 2013 is that this is the first month its been necessary to combine BEV sales for them to outpace PHEV sales vs just comparing LEAF vs PHEV sales.
I used hybridcars.com as a source for my sales comparisons.