Copy Point From Tikz to Tkz

You can always extract the coordinates of a point and use them. This can be used to define a macro that "copies" TikZ points to tkz. (Note that this version of the macro assumes you did not customize the coordinates, i.e. you didn't redefine x nor y.)

\documentclass[tikz]{standalone}
\usepackage{tkz-euclide}
\usetikzlibrary{intersections}
\newcommand{\CopyPointToTkz}[2]{\path (#1);
    \pgfgetlastxy{\macrox}{\macroy}
    \pgfmathsetmacro{\macroxcm}{\macrox/1cm}
    \pgfmathsetmacro{\macroycm}{\macroy/1cm}
    \tkzDefPoint(\macroxcm,\macroycm){#2}
}
\begin{document}
 \begin{tikzpicture}
    \tkzDefPoint(1,1){A}
    \node at (A){A};
    \draw[name path=line1] (A) -- (4,2);
    \draw[name path=line2] (2,0) -- (2,4);
    \fill[name intersections={of=line1 and line2, by={B}}] (B) circle (2pt);
    \CopyPointToTkz{B}{CopyOfB}
    \node at (CopyOfB){B};
 \end{tikzpicture}
\end{document}

If you want to allow for arbitrary redefinitions of the coordinate system, you need to go a bit more complicated.

\documentclass[tikz]{standalone}
\usepackage{tkz-euclide}
\usetikzlibrary{intersections}
\makeatletter
\newcommand{\CopyPointToTkz}[2]{\path (#1);
    \pgfgetlastxy{\macrox}{\macroy}
    \pgfmathsetmacro{\macroxcm}{\macrox/1cm}
    \pgfmathsetmacro{\macroycm}{\macroy/1cm}
    \pgfmathsetmacro{\mya}{\pgf@xx/1cm}
    \pgfmathsetmacro{\myb}{\pgf@yx/1cm}
    \pgfmathsetmacro{\myc}{\pgf@xy/1cm}
    \pgfmathsetmacro{\myd}{\pgf@yy/1cm}
    \pgfmathsetmacro{\mydet}{\mya*\myd-\myb*\myc}
    \pgfmathsetmacro{\myxx}{\myd/\mydet}
    \pgfmathsetmacro{\myxy}{-\myc/\mydet}
    \pgfmathsetmacro{\myyx}{-\myb/\mydet}
    \pgfmathsetmacro{\myyy}{\mya/\mydet}
    \tkzDefPoint(\macroxcm*\myxx+\macroycm*\myyx,\macroxcm*\myxy+\macroycm*\myyy){#2}
}
\makeatother
\begin{document}
 \begin{tikzpicture}[x=2cm]
    \tkzDefPoint(1,1){A}
    \node at (A){A};
    \draw[name path=line1] (A) -- (4,2);
    \draw[name path=line2] (2,0) -- (2,4);
    \fill[name intersections={of=line1 and line2, by={B}}] (B) circle (2pt);
    \CopyPointToTkz{B}{CopyOfB}
    \node at (CopyOfB){B};
 \end{tikzpicture}
\end{document}

It's possible with intern macros from tkz-euclide (page 128 of the new documentation 3.05 Miscellaneous tools)

\documentclass[tikz]{standalone}
\usepackage{tkz-euclide}
\usetikzlibrary{intersections}

\begin{document}
    \begin{tikzpicture}
    \tkzDefPoint(1,1){A}
    \node at (A){A};
    \draw[name path=line1] (A) -- (4,2);
    \draw[name path=line2] (2,0) -- (2,4);
    \fill[name intersections={of=line1 and line2, by={B}}] (B) circle (2pt);
    \tkzGetPointCoord(B){V}
    \tkzDefPoint(\Vx,\Vy){copyB}
     \tkzDrawPoint[red](copyB)
    \end{tikzpicture}
\end{document}