MetaPost and fonts

[Jens-Uwe Morawski <morawski@gmx.net>]

Ahoi,

in a document i use the following font-setup:
\enableregime[il1]
\usetypescriptfile[ts-larabie]
\definetypeface[BlueHighway][ss][sans][BlueHighway][default]
	[rscale=1.3,encoding=ec]
\setupencoding[default=ec]
\setupbodyfont[BlueHighway,ss,10pt]

\usetypescriptfile[ts-misc-ttf]
\definetypeface[Binky][rm][serif][Binky][default][encoding=texnansi]

In the normal text now the default-font is BlueHighway and i can
switch temporally to Binky using {\Binky <some text>}.

Using the above font-setup in \start|\stopMPenvironment sets
correctly the body-font, but a

label(btex some {\Binky important} words etex,origin)

fails, since the command \Binky is unknown.

In contrast the following stand-alone MP-file works.
(You have to setup MetaPost so that it uses texexec for processing
  the generated mpxerr.tex (mpost --tex=texexec or env-var TEX=texexec))

%--snip---
input metafun ;

verbatimtex
\usetypescriptfile[ts-larabie]
\definetypeface[BlueHighway][ss][sans][BlueHighway][default]
	[rscale=1.3,encoding=ec]
\setupencoding[default=ec]
\enableregime[il1]
\setupbodyfont[BlueHighway,ss,10pt]

\usetypescriptfile[ts-misc-ttf]
\definetypeface[Binky][rm][serif][Binky][default][encoding=texnansi]
\starttext
etex

beginfig(1);
label.top(btex Some text in BlueHighway (default). etex, origin) ;
label.bot(btex \Binky  Some text in Binky etex, origin);
endfig;

verbatimtex
\stoptext
etex
end
%---snap----

I thought that ConTeXt generates a file like this to process
the inline MetaPost code, but it seems that i do not understand
the ConTeXt-MP-processing. 

What can i do to have the full typesetting/font-setup capabilities
also available in MetaPost?

Thanks in advance.

Jens