At T-15, anyone who has not 'presented at the gate' cab be offloaded and ones' seat offered to standby passengers. If you are still on your connecting flight at T-15, it is difficult to envision how you will present at the gate at T-15.

Until UA gets the secret weather control application that DL has, it will continue to treat weather delays as 'out of their control' and ergo no compensation will be offered (nws 1K and GS fliers)