`start-process` in Emacs on Windows seems to mangle process output

[evgeniy . sharapov]

Here's the my problem. When I run

------------------------------------------------------------------
(let ((default-directory "C:/Users/esharapov/.emacs.d/"))
  (apply 'start-process "ag" (get-buffer-create "test")
         "c:\\App\\emacs\\libexec\\emacs\\24.5\\i686-pc-mingw32\\cmdproxy.exe"
         (list "-c" "\"ag\" \"--nocolor\"  \"--literal\" \"--line-number\" 
\"--smart-case\" \"--nogroup\" \"--column\" \"--stats\" \"--\" \"keymap-on\" 
\".\"")))
------------------------------------------------------------------

I get in the buffer following output: 

------------------------------------------------------------------
194:15:    (defmacro keymap-on-key (name keys)
233:9:       (keymap-on-key ctl-x-f-map "C-x f")
572:7:     (keymap-on-key ctl-z-w-map "C-z w")
194:15:    (defmacro keymap-on-key (name keys)

233:9:       (keymap-on-key ctl-x-f-map "C-x f")

572:7:     (keymap-on-key ctl-z-w-map "C-z w")

6 matches
382 files searched
8993756 bytes searched
0.446822 seconds

Process ag finished
------------------------------------------------------------------

However when I run it in the Windows command prompt as

------------------------------------------------------------------
c:\\App\\emacs\\libexec\\emacs\\24.5\\i686-pc-mingw32\\cmdproxy.exe /c 
"C:\\App\\bin\\ag.exe --nocolor  --literal --line-number --smart-case --nogroup 
--column --stats -- keymap-on ."
------------------------------------------------------------------

I get the following output 

------------------------------------------------------------------
#configuration.org#:194:15:    (defmacro keymap-on-key (name keys)
#configuration.org#:233:9:       (keymap-on-key ctl-x-f-map "C-x f")
#configuration.org#:572:7:     (keymap-on-key ctl-z-w-map "C-z w")
configuration.org:194:15:    (defmacro keymap-on-key (name keys)
configuration.org:233:9:       (keymap-on-key ctl-x-f-map "C-x f")
configuration.org:572:7:     (keymap-on-key ctl-z-w-map "C-z w")
6 matches
382 files searched
8993756 bytes searched
0.483917 seconds
-------------------------------------------------------------------

Notice when I use 'start-process' the file name is being removed from the 
process output. Does anyone know what's the issue here ?
Is it a bug or a feature that could be turned off  ?

Versions:
Microsoft Windows [Version 6.3.9600]
GNU Emacs 24.5.1 (i686-pc-mingw32) of 2015-04-11 on LEG570


Sincerely yours,
    Evgeniy Sharapov