Build-completion using imenu search hits

[Nordlöw]

How can I programmatically access the hits from the search done by
imenu using for example

(defconst bjam-imenu-generic-expression
  `(
    ("Executables" ,(concat "^\\(exe\\)" "[[:space:]\n]+" "\\([A-Za-
z0-9_/.]+\\)" "[[:space:]\n]+" ":") 2)
    ("Libraries" ,(concat "^\\(lib\\)" "[[:space:]\n]+" "\\([A-Za-
z0-9_/.]+\\)" "[[:space:]\n]+" ":") 2)
    ("Projects" ,(concat "^\\(project\\)" "[[:space:]\n]+" "\\([A-Za-
z0-9_/.]+\\)" "[[:space:]\n]+" ":") 2)

    ;; 
http://www.boost.org/doc/libs/1_38_0/doc/html/bbv2/tasks.html#bbv2.reference.precompiled_headers
    ("Precompiled C Headers" "^c-pch[[:space:]\n]+\\([A-Za-z0-9_/.]+\\)
[[:space:]\n]+:" 1)
    ("Precompiled C++ Headers" "^cpp-pch[[:space:]\n]+\\([A-Za-z0-9_/.]
+\\)[[:space:]\n]+:" 1)

    ("Rules" "^rule[[:space:]\n]+\\([A-Za-z0-9_]+\\)" 1)
    ("Actions" "^actions[[:space:]\n]+\\([A-Za-z0-9_]+\\)" 1)
    )
  "Imenu generic expression for BJam mode.  See `imenu-generic-
expression'.")
;; Use: (nth 1 (assoc "Executables" bjam-imenu-generic-expression))

in bjam-mode.el. I wan't to use this to provide build/clean target
completion from the menu.

Thanks in advance,
Per Nordlöw