Our local power company provides a small code book of their own. I couldn't find a rule concerning placement near window. In the past I've installed meter enclosures less than three feet from window and had no problem with it passing elec. inspection. Mounting height must be five to six feet.
I believe this clearance issue is rooted in 230-9, which requires claerance for open conductors without an overall jacket. The service drop, which is spliced at the service head is typically open conductors, and therefore subject to the clearance requirements. The service entrance conductors, which may be jacketed SE Cable would not be subject ot the clearances due to the overall jacket, and may pass closer to windows etc. This probably would apply to the meter socket as well, unless local or utility rules prohibit it.