If you didn't have the ^0x80 then the assembler would give the following warning,
"Message[302] : Register in operand not in bank 0. Ensure that bank bits are correct."
This is because TRISA has the value 0x85 (bank 1) and the largest allowable value if 0x7f. The ^0x80 converts 0x84 into 0x04 - another way to do this is &0x7F.
As long as you set/clr the bank select bits properly you can ignore this message. Another way to get rid of this annoying message is to do "errorlevel -302".