What is line to line voltage supposed to meter at?
Here are common arrangements in the US and Canada, taken from a cached FAQ from Schneider Electric:



The 120/208VAC is common in residential complexes and some commercial situations (not ordinary houses, where single phase 120/240 is standard). In industrial installations you find other 3-phase options. For example, in one building I frequent the office lights operate from 347VAC, but phase-to-phase is 600VAC (Canada) so relatively heavy equipment such as screw compressors can be used. 277/480 would likely be used in the US. 

Probably some huge houses are wired with 120/208 line-to-line. 

As you can see, there are a few delta options with 240VAC.