I'm looking for a word that refers to folks who are "plugged in" or "knowledgeable and connected" to some network of people and information. The "authorities" often connotes law enforcement and therefore doesn't fit well.
The Illuminati is a nice term that describes a community of people with a special/secret knowledge. (Unfortunately, it has been somewhat soiled in recent times by conspiracy theorists and is now most commonly used to label a supposed 'secret society' controlling world governments/media/etc.)
Enlightened comes from the same root and describes people endowed with a certain knowledge/understanding. This word often appears in religious context but by no means is it limited to that.
A person with esoteric knowledge is someone who knows/understands something which only a select few know/understand. Here, rather than being members of a secret society, the 'select few' are simply those who have studied the topic in question.
The Intelligentsia is a term used to refer to intellectuals of a high social class involved in cultural/educational development, creative labour.
If we remove that sense of special/privileged, I suppose any of the following could also work, depending on your specific context:
Nouns: Contributor; Member; Scholar; Academia;
Adjectives: Learned; Erudite;
Most of these latter words tend to relate to either knowledge or connectedness, rather than both. A dictionary should help you with their specific uses.
Hope that helps.
Such folks are in the know or in the loop:
An appropriate single word would be the group noun, the initiated:
cabal - is a great word with negative, conspiratorial connotations,
cabalist - an expert who is highly skilled in obscure or difficult, esoteric matters.
These are (mostly) single word terms meaning those who are plugged in. Some are nouns, others are adjectives, but I think that is within the scope of the question.
Cognoscenti n. To be one of those in the know
Au courante adj. Well-informed about the latest trends, most current news
Up-to-date adj. Current
Ear to the ground: This is an idiom. It means to be alert to any changes, immediately.
On point: Also an idiom, implying an alert status
Insider n. A member of the inner circle, Star Chamber, cabal of those who have a need-to-know
Hip adj. The ultimate term for being plugged in: To be hip to something IS to be well-informed.