Actually, I do need TPMS sensors. I have replaced them personally on my current wheels.
The M3's definitely use the rotational speed method of monitoring. The non-M E46's that came with RFT from factory (usually on the sports package option - but not always), indeed uses RDC with TPMS sensors in each wheel. If you look in the driver's door jam above the sticker that tells you GVW and recommended tire psi, those that have the actual RDC/TPMS system will have an RDC sticker as well indicating the module code.
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