hello i did a search and i didin't find anything.
a year ago , i faction changed from an orc to a dwarf. then a couple of month ago i decided to go back to the horde , i faction changed to a belf .as i was playing i decided to get my of silvermoon title by becoming a champion of silvermoon , but as i got to the tourney , both the orc and belf npc's offered me quests and i was able to become a champion of orgrimmar.
tl;dr : if you faction change from say orc to any alliance race then back to say a blood elf , the orc quests are still available.
i was not sure when to put this so feel free to move it if its the wrong spot.