Is there a required spacing between where high and low voltage lines attach to a house?
Since there are slight differences depending on what type of communications systems we're talking about, we'll have to look at a few different sections.
NEC 2008
Article 800 Communications Circuits

800.44 Overhead Communications Wires and Cables.
(A) On Poles and In-Span.
(4) Clearance. Supply service drops of 0–750 volts running above and parallel to communications service drops shall have a minimum
separation of 300 mm (12 in.) at any point in the span, including the
point of and at their attachment to the building, provided the
non-grounded conductors are insulated and that a clearance of not less
than 1.0 m (40 in.) is maintained between the two services at the
pole.

Article 810 Radio and Television Equipment

810.13 Avoidance of Contacts with Conductors of Other Systems. Outdoor antennas and lead-in conductors from an antenna to a building
shall not cross over open conductors of electric light or power
circuits and shall be kept well away from all such circuits so as to
avoid the possibility of accidental contact. Where proximity to open
electric light or power service conductors of less than 250 volts
between conductors cannot be avoided, the installation shall be such
as to provide a clearance of at least 600 mm (2 ft). Where
practicable, antenna conductors shall be installed so as not to cross
under open electric light or power conductors.

Article 820 Community Antenna Television and Radio Distribution

820.44 Overhead Coaxial Cables.
(B) Lead-in Clearance. Lead-in or aerial-drop coaxial cables from a pole or other support, including the point of initial attachment to
a building or structure, shall be kept away from electric light,
power, Class 1, or non–power limited fire alarm circuit conductors so
as to avoid the possibility of accidental contact.
Exception: Where proximity to electric light, power, Class 1, or non–power-limited fire alarm circuit service conductors cannot be
avoided, the installation shall be such as to provide clearances of
not less than 300 mm (12 in.) from light, power, Class 1, or
non–power-limited fire alarm circuit service drops. The clearance
requirement shall apply at all points along the drop, and it shall
increase to 1.02 m (40 in.) at the pole.

Article 830 Network-Powered Broadband Communications Systems

830.44 Aerial Cables.
(C) Lead-in Clearance. Lead-in or aerial-drop network-powered broadband communications cables from a pole or other support,
including the point of initial attachment to a building or structure,
shall be kept away from electric light, power, Class 1, or
non–power-limited fire alarm circuit conductors so as to avoid the
possibility of accidental contact.
Exception: Where proximity to electric light, power, Class 1, or non–power-limited fire alarm circuit service conductors cannot be
avoided, the installation shall be such as to provide clearances of
not less than 300 mm (12 in.) from light, power, Class 1, or
non–power-limited fire alarm circuit service drops. The clearance
requirement shall apply to all points along the drop, and it shall
increase to 1.02 m (40 in.) at the pole.


tl;dr.
Telephone (Communication Systems)

12&quot; (300 mm) at any point of the span.
12&quot; (300 mm) at the point of attachment.
40&quot; (1 m) at the service pole.

Antenna (Radio and Television Equipment)

Kept away if possible.
Should not cross over or under.
2' (600 mm) if proximity can't be avoided.

Cable (Community Antenna Television and Radio Distribution)

Kept away if possible.
12&quot; (300 mm) if proximity can't be avoided.
40&quot; (1.02 m) at the service pole.

Broadband (Network-Powered Broadband Communications Systems)

Kept away if possible.
12&quot; (300 mm) if proximity can't be avoided.
40&quot; (1.02 m) at the service pole.