RE:Holding up
There may not be any one single reason for the sudden increase (which was not huge in any case). It may be simply a case of analysts and institutional investors catching up on the series of reasonably good news (refinancing at favorable rates, sale of fine papers division, stable to lower OCC prices...). When all this is put together, it may have become clear that CAS was undervalued at $6-6.50 per share.
The second quarter just ended and some leaks on the results are not unconceivable (although I have never seen evidence of this in CAS' case).
Finally, the chances of a takeover are very slim to zero: the controlling shareholders will want to hold on to their company for may years to come.