If located at 4000, how does the reset vector get activated?

Actually, it does put the reset vector at 0x0000, and it contains a LJMP to somewhere in the 2K space above 0x4000; eg,

LINK MAP OF MODULE:  abstrptr (ABSTRPTR)

            TYPE    BASE      LENGTH    RELOCATION   SEGMENT NAME
            -----------------------------------------------------

            * * * * * * *   C O D E   M E M O R Y   * * * * * * *
            CODE    0000H     0003H     ABSOLUTE     
                    0003H     3FFDH                  *** GAP ***
            CODE    4000H     0071H     UNIT         ?C?LIB_CODE
            CODE    4071H     0022H     UNIT         ?PR?MAIN?ABSTRPTR
            CODE    4093H     000CH     UNIT         ?C_C51STARTUP

Presumably it'd do something similar with the interrupt vectors?