Redirect output of Shell-Helper "Table" into a string

My Cake-Shell is also sending an email - and I want to send a simple formated table (text-only, not as html-table).
Is it possible to redirect the output of a Shell-Helper into a String?
As a workaround, I “forked” it as new helper - but this does not make me happy.
It seems, that it is not possible to use “ob_start()” in conjunction with $this->out() (which works with “debug()”.
Or - to be more general:: is it possible to redirect “$this->out” into a string (like ob_start())

Thank you in advance.