Large commercial premises requiring heat from their car park.

New airports heating their terminals from the runway, or providing a de-iced runway.

Housing developments, pre-heating water from drives and cul-de-sacs to low temperature heating systems such as underfloor heating.

Using under-tarmac heating for roads makes sense in de-icing the road and maintaining a temperature less stressful to the asphalt, but to transport heat energy to home and industry would be difficult … unless a series of heat exchangers turned the marginal heat from the ground source to electricity perhaps with the help of small scale traditional fossil fuel power stations. I just envisage pipes from the road going into peoples homes.

1. with regards to the heat softening the asphalt this is true as asphalt remains a fluid the viscosity of which obviously decreases as it heats up. This idea will actually reduce this effect by absorbing the heat generated by the sun and removing it in the fluid to be used else where.
2. the problem of the flexibility of the asphalt under heat and pressure from heavy vehicles can be over come by using heavy grades of black high pressure PVC Split I section piping which when imbeded in the asphalt I believe will support the external pressures when the fluid is pumped through in a closed circuit system under high pressure and using heat exchangers to recover the latent energy.
3. the best application of this technology would be in new housing development as the technology can be installed in the initial construction and included in the site development costs split over each unit constructed and off set by the new owners energy savings.
4. the technology would be hard pressed to make an impact on commercial or industrial use unless incorporated into the external wall and roof of the structures during construction. Which I have done in an agricultural application with fair success.