One thing of note is that 1000-base-T and G.991 (marketed as SHDSL/HDSL/SDSL depending on country/telco) is somewhat similar technology that is hard to classify as being baseband or broadband. One of my somewhat more absurd networking experiences was using SHDSL as “LAN with cheap wire” on anime convention. We had few hundred meters of flat phone “tinsel wire” left over from previous project and I had somehow acquired bunch of Cisco 17xxs and WIC-1SHDSL line cards. It worked well enough for our purposes and I learned one thing: plain G.991 works over random wire reasonably, while G.991bis with enabled channel bonding does not (probably because of crosstalk).

Edit: one notable thing was that we tested the whole setup beforehand with same cables, but coiled. And all the links were capable of at least 3Mbps. Once we unraveled the cables on the site most of the links were unable to train at more than 512kbps in two-pair mode, but worked reliably at 1.5Mbps in single-pair mode.