justin: I'm just about positive that ain't gonna work.
DSL signals are higher in frequency than the ones that you normally use with your phone. that's why they can coexist on the wire with your phone line. the filter is just there to make sure those high frequencies don't do anything weird to your phones i think.
so on the other end of the phone line, they probably have a similar splitter, hooking the high frequency band up to something like another dsl modem, and the low freq band up to the normal phone hardware on the other end
trouble is, a regular phone modem is designed to operate at the same low frequency as the voice band that you use - and it also doesn't require them to have any special hardware on the other end of the line because of this.
So I'm pretty darn sure it isn't going to work, sorry