heteroplasmy of cloning vectors

[G]

This may be a stupid question but it occured to me this week whilst I
was trying to clone a PCR product. Is it possible for transfomed cells 
to be heteroplasmic, i.e. to contain different species of plasmid perhaps
one type with an insert and one without? I want to clone a PCR product to
 use as an internal standard, if heteroplasmy occurs then my calculated 
copy number will be elevated due to the possible presence of plasmids with 
no insert.
G Jenkins