Yes, in theory it is possible to prevent these kinds of infections without resorting to secure boot (e.g., by insisting that all the suppliers of components of the motherboard start designing components that cannot be pwned) but so far all the computers you have actually been able to buy that are immune to these kinds of infections achieve that immunity with secure-boot technology.
The BMC usually has full access to system memory as well, so if you can get the timing right, you could replace the secure boot verified image with your own after verification.
Also, re: BusinessWeek, hey look a hardware backdoor installed on servers. Pretty sure IPMI vulnerability fits the bill for most of what was described.