Very, very simply, there are four main cost elements in a "line":
1. The DSL modem that connects your PC/LAN to the exchange at the CO (central office), ie exchange. This cost is borne by the subscriber. If your ISP gives you a "free" modem, you're still paying for it, though the cost isn't itemized.
2. The twisted pair copper ("last mile") from the exchange to your premises. This has to be installed and maintained.
3. Connecting the aggregated subscriber data streams to the ISP - done through a Digital Subscriber Line Access Multiplexer (DSLAM).
4. At the ISP, the aggregated data streams are routed to a Broadband Remote Access Server (B-RAS), which is used to validate things like account and access credentials, after which the data are routed into the internet.
There will always be a charge for the copper line to your premises. If there isn't, who pays when it gets damaged or stolen? The CO will always charge to suck off and aggregate the various DSL data streams and route and carry them to the ISP's B-RAS.
There will always be a charge for connecting to the DSLAM (manufacturers do not provide them free of charge, therefore Telkom cannot either).
The current Telkom network architecture and accounting system links you the subscriber to the DSLAM by means of a telephone account number.
Even if we get naked DSL in SA, you'll still pay Telkom for the wire between your premises and for the DSLAM. And you'll separately pay your ISP for their portion. The only change it would make is an admin one - instead of getting a telephone number and voice service bundled in by Telkom you'd get a different account number and a line that isn't connected to the voice network. This might save R1 a month, though Telkom would have to spend (and recover from you) the money needed to make the changes to their accounting and billing system.
Hope that clarifies it a little.