There are drivers from Mediafour and Paragon that will allow you to get R/W access to HFS(+) partitions under Windows.
Time Machine uses sparse bundles to store backup files if used over a network, so theoretically you can store it on any partition type with any OS. However, Apple only allow you to use it over AFP and there are checks to prevent non-Time Capsule devices being used.
You can hacks around this, but that also means if your system crashes, you'll have to reinstall first before you can restore anything. (Also note TM backup to an external hard disk may be in a different format, so if you will not be able to access your old backups over the network.)
In the end most of such questions ends with an answer like use
rsync instead (and it really is a more flexible and though more involving solution).