...dirty hack...

\newdimen\spaceleft
\def\pagespace{%
\ifdim\pagetotal=0pt
\spaceleft=\textheight
\else
\spaceleft=\pagegoal
\advance\spaceleft by -\pagetotal
\fi}
\def\RuleToEnd{
\pagespace
\newdimen\Temp
\newcount\Tempc \Tempc=\numexpr\rowTBL+1\relax
\dorecurse\Tempc{
\advance\Temp by \dimexpr\gettblht{\recurselevel}{1}\relax}%
\advance \spaceleft  by -\Temp%
\advance \spaceleft  by -1pt%
% funny
%\llap{\vbox to 0pt{\hsize=11pt\vss\vrule width11pt height\Temp}}
\vrule width0pt height\spaceleft%
}

\bTR[after={\RuleToEnd}]