Although I do not have details, I believe the request was for more than just the Makefiles. I believe the request was for the instructions necessary to install the resulting binaries on the device. While the GPL v2 does say "scripts for ... installation", not everyone interprets that as installation to the device. In particular, one of the primary maintainers of busybox, Eric Anderson has told me he does not interpret the GPL v2 license to require that. It would be nice to get more legal details here, but the sued parties are being understandable tight-lipped.
I know some people in the community want to be Draconian about anti-Tivo-ization, but personally I just don't think the license requires it, and that this extra push for device installation access on a GPL v2-licensed component is doing more harm than good. I have heard that at least one company has backed off the use of Linux over it.