alias no working (in a specific context)

[sdouglas]

Configuration Information [Automatically generated, do not change]:
Machine: sparc
OS: solaris2.5.1
Compiler: gcc
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='sparc' 
-DCONF_OSTYPE='solaris2.5.1' -DCONF_MACHTYPE='sparc-sun-solaris2.5.1' 
-DCONF_VENDOR='sun' -DSHELL  -DHAVE_CONFIG_H -DSunOS5  -I.  -I. -I./include 
-I./lib -I/usr/local/include -g -O2
uname output: SunOS threeofsolaris 5.6 Generic_105181-22 sun4u sparc 
SUNW,Ultra-5_10
Machine Type: sparc-sun-solaris2.5.1

Bash Version: 2.04
Patch Level: 0
Release Status: release

Description:
        The alias 'hi' doesn't work in the following example.
        This may be another symptom of a bug I reported a couple months ago
        involving aliases and BASH_ENV (but which I can no longer find
        on Deja).

Repeat-By:
        Run this script:

            shopt -s expand_aliases
            alias hi='echo hi'

            f() {
              hi $1                #1
              t="$(hi there $1)"   #2
              echo $t
            }

            f 1     # works
            f 2 &   # works
            (f 3)   # works
            (f 4) & # line #2 fails in this case
            wait