I realize that the bulleted descriptions I wrote could be inferred as an firm endorsement of T1 over DSL. This isn't the case, however, there are salient differences:
> T1 delivers lower speed than today's range of xDSL offerings, but it's constant, bidirectional speed that isn't subject to external influences. Consumer DSL speed varies from day to day - old cable, rodent damaged cable, oversubscription, wet weather, hot weather... T1 forfeits less throughput to overhead than ADSL does: my Qwest/C-Link ADSL's Up to 1.5 label should really be Up to 1.3 On a Good Day.
> If a T1 goes down, the serving telco attends to it immediately, as specified by contract. Read anywhere else in these forums about how diligently most telcos do or do not respond to subscribers' DSL outages and slowdowns. Again, the descriptive phrase for consumer DSL service is "best effort".
Ironically, these days, most T1 spans are carried ("provisioned") between central offices and subscribers on 2- or 4-wire HDSL. However, these HDSL links are proprietary to the phone company - if there's a failure the telco gets right on it, in my experience, unlike consumer-class xDSL. In contrast, when responding to a complaint made about a flaky consumer ADSL, I've heard a telco field tech say to the subscriber, "We don't make enough money on it to justify spending any time on it [to get it to work properly]." They never say this to a T1 subscriber.
Going back to the OP, the situation is that a signed Cbeyond contract may compel using the dedicated T1, like it or not. If so, I would make the best of a costly misstep by aggregating it with whatever services the company could comfortably afford in addition to the cost of the T1: one or two DSLs and the highest-speed business-class cable offering, to enhance reliability through diversity. When a problem occurs, it's easier to tell the tenants that the connection will be "a little slow" until it's fixed, as opposed to having to confess that their internet will be out entirely for an unknown length of time. Once people get used to a service, free or not, they expect it to be there all the time.