The organization depends on the size of the unit it is assigned to. A division had a MI battalion assigned. Wiki has a good description of a divisional battalion in the 90s at
http://en.wikipedia.org/wiki/140th_M...United_States) . That's for a heavy division, a light division's bn was organized similarly, but with HMMWVs instead of M-113 series vehicles. An alternative organization, adopted later in the 90s, is for a HQ company, three direct support companies, each organized with an I&S, C&J and EW platoon (each assigned to one of the division's combat brigades), a general support company (a larger version of the direct support company that supported the division commander) and the LRSD. The MI company assigned to an independent bde or regiment was more or less like one of the direct support companies.
At Corps and higher levels I'm not as sure. Each corps had a LRS company assigned, and you also start adding other assets, like fixed-wing surveillence aircraft (Mohawks, C-12s and the like, not U-2s!).
As for what they would be doing in T2k, a few ideas. The primary mission is to provide the unit commander information about what the enemy is able and possibly even likely to do. The LRSDs and GSRs go fairly deep behind enemy lines - 30-50km or so - and call in air strikes and MLRS, ATACMS and artilery strikes and feed info about approaching enemy units. The EW units try to locate enemy HQs, artillery batteries and the like by locating their radios, while the C&J (collection & jamming) guys try to listen in and/or jam enemy radio nets. The I&S guys have 2 roles - the GSR (Ground Surveillence Radar) guys are behind the lines doing the same thing as the LRSDs, while the CI (Counterintel) guys are interrogating prisoners of war and possibly coordinating with the MPs about folks wandering around the division area. That's about it at the division level. At the Corps and higher level, the missions are about the same, but they're looking deeper behind enemy lines. There are also detachments that coordinate, share and analyse the data to feed into commander's G/J/S-2 staffs. All in all, not the sort of sinister, James-Bond operations (or the oxymoron) that pop into most people's minds when "Army Intelligence" is mentioned...