braces on the sides of an easybmat matrix

Do you mean something like this?

\documentclass{article}
\usepackage{easybmat}
\begin{document}
\[ 
M(z)= \left[
\begin{BMAT}[5pt]{c|c}{c}
\underbrace{\left.\begin{BMAT}[5pt]{c:c:c}{ccccccc}
& & \\
& & \\
& & \\
v_1 & \dots & v_m \\
& & \\
& & \\
& &
\end{BMAT}\right\}6}_5
&
\begin{BMAT}{c}{c|c}
\begin{BMAT}[5pt]{c:c:c}{ccc}
& & \\
w_1(a) & \dots & w_n(a) \\
& &
\end{BMAT}
\\
\begin{BMAT}[10pt]{c}{c}
B(z)
\end{BMAT}
\end{BMAT}
\end{BMAT} 
\right]
\]
\end{document}

(If you do mean something like that, the positioning of the braces would need some adjustment, but that's easily done if this is basically what you need)

For the vertical braces, you can use the bigdelim package; the horizontal braces were made using \underset and \underbrace and a "rule" of variable width and no height:

\documentclass{article}
\usepackage{amsmath}
\usepackage{easybmat}
\usepackage{multirow,bigdelim}

\newcommand*\hexbrace[2]{%
  \underset{#2}{\underbrace{\rule{#1}{0pt}}}}

\begin{document}
\[ 
M(z)= 
\begin{array}{c@{}c}
\left[
  \begin{BMAT}[5pt]{c|c}{c}
    \begin{BMAT}[5pt]{c:c:c}{ccccccc}
      & & \\
      & & \\
      & & \\
      v_1 & \dots & v_m \\
      & & \\
      & & \\
      & &
    \end{BMAT}
    &
    \begin{BMAT}{c}{c|c}
      \begin{BMAT}[5pt]{c:c:c}{ccc}
        & & \\
        w_1(a) & \dots & w_n(a) \\
        & &
      \end{BMAT}
      \\
      \begin{BMAT}[10pt]{c}{c}
        B(z)
      \end{BMAT}
    \end{BMAT}
  \end{BMAT} 
\right] 
& 
\begin{array}{l}
  \\[-8mm] \rdelim\}{4}{6mm}[$J$] \\ \\ \\[4mm]  \rdelim\}{3}{6mm}[$H$] \\ \\
\end{array} \\[-1ex]
\hexbrace{2.7cm}{m}\hexbrace{3.8cm}{n}
\end{array}
\]

\end{document}