It will "work" to conduct electricity, hey its three conductors, BUT THATS NOT ITS INTENDED NOR NEC PROPER USE!!!!!!!!!!!!
1) First of all, it has ONLY two insulated conductors plus a bare conductor. Its intened to supply 120/240 volt single phase three wire service from typically a pole mounted utility transformer to the home service entrance panel and the 2 UnGrounded Conductors are insulated while the Grounded Neutral Conductor is bare.
2) Its ampacity would have to be derated if it were enclosed in conduit as its labeled ampacity assumes its in free open air.
3) Far as I know (but NO warranty Im Code rusty) if you run an equipment GroundING Conductor inside an underground conduit IT NEEDS TO BE INSULATED AND NOTTTTTTTTTTTTTT BARE
THEREFORE you couldn't (if the NEC matters to you) use it underground in conduit for even 120 volt ONLY service because the 2 insulated conductors would have to be Hot UngrounDED Conductor and the Neutral Grounded Conductor BUT WHAT ABOUT THE NEED (as far as NEC is concerned) FOR AN INSULATED EQUIPMENT GROUNDING CONDUCTOR??? All you have left is that bare (intended for Neutral) conductor.
BUT NOTE IT WILL WORK its your money and your call NOT any of us here and it will work even if NOT Code proper, so do as you please. Its still three conductors and each will conduct electricity and I'm sure Billy Bob and Bubba and many others have done it before and YES IT WORKS
NOTE Once more I'm basing my answer on my "belief" that you need to use an insulated GroundING Equipment Conductor in underground conduit (if NEC matters that is) and if that's NOT true you could get by with the bare conductor for use as the Equipment GroundiNG Conductor in which case 120 volt single phase service could be supplied in underground conduit PROVIDED THE AMPACITY IS DERATED SINCE ITS NOT IN FREE AIR!!!!
Another thought, I don't think twisted triplex is NEC permissible underground at all !! for that you need UF (Underground Feeder) or USE (Underground Service Entrance) cable NOT aerial twisted triplex!!!
STILL YESSSSSSSSSS IT WOULD "WORK"
Best wishes n God Bless
John T Too long retired Electrical Engineer and code rusty so no warranty !!