A B737-800 FLC IS QUERIED BY ATC AS TO THEIR RTE AS CTLR HAS TO ISSUE A DSCNT CLRNC TO ACR Y WHO IS OPPOSITE DIRECTION SAME ALT TFC IN CTL SECTOR OF ZHU; TX.

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ATC OUT OF THE IAH AREA WAS HEAVILY SATURATED DUE TO REROUTES; WX; ETC. WE WERE REROUTED ON A TRIP FROM IAH TO PVR. NORMALLY WE WOULD GO THE PSX J29 RTE OVER MTY; FLT PLAN RTE. BUT AGAIN DUE TO WX AND TFC WE WERE SENT DIRECT IDU DIRECT CWK DIRECT MTY FLT PLAN RTE. WE MADE OUR TURN SBOUND AT CWK TO MTY. ABOUT 40 MI S; ZHU ASKED WHERE WE WERE GOING AND I READ BACK OUR CLRNC TO HIM. HE DID NOT KNOW WE HAD BEEN CLRED TO DO THAT. I DON'T KNOW WHERE HE THOUGHT OUR DEST WAS; BUT HE SAID HE THOUGHT WE WERE GOING TO PROCEED ON W TOWARDS JCT WITH ALL THE OTHER TFC. ACCORDING TO HIM; HE WAS NOT INFORMED OF OUR CLRED RTE BY THE PREVIOUS SECTOR. SO WHEN WE TURNED S TOWARDS MTY 'AS CLRED' IT PUT US IN A POTENTIAL CONFLICT WITH AN ONCOMING ACR Y (A B737) AT OUR ALT; FL220. ACR Y WAS CLRED TO DSND EXPEDITIOUSLY TO FL210 AND WE WERE TOLD TO TURN R TO A 310 DEG HDG. THIS AVOIDED THE CONFLICT AND TCASII DID NOT GIVE A TA OR RA. THE PROB SEEMS TO HAVE COME FROM A LACK OF COM BTWN VARIOUS ATC SECTORS. OR IN OTHER WORDS; THE L-HAND NOT KNOWING WHAT THE R-HAND WAS DOING.