Congratulations to the winner.

In this week edition, I spy with my little eye answer is INFRASTRUCTURES based on it clues;

It is a 15-letter word

INFRASTRUCTURES is a 15-letter word and it means a physical facilities serving a country or community. Examples are transportation systems, communication networks, sewage, water and school systems.

It's the fundamentals for many things

Investing on the fundamental infrastructure projects boost the economy of a society.

It is interconnected

Infrastructure plays a vital role in the socio-economic development of a nation.

isPrivate ≡ !isPublic

Infrastructure is both private and public. The public infrastructure projects are created, owned and maintained by the government while the private infrastructure projects are private investment by individuals in a public works.