Are the compact objects in supernova remnants isolated neutron stars? It seems all the central compact objects correlated with supernova remnant(SNRs) are isolated, not in binaries, right? 

I find only one exception. A source is claimed to be a compact binary which correlates with SNR G308.3-1.4.ads link

My question is, generally, are the compact objects in SNR always isolated? 
And observationally, are the compact objects in SNRs neutron stars?
There are plenty of hard-x-ray binaries that involve a compact object with a companion.  Some should be in supernova remnants, but I don't know how many.  Are you sure there is a problem?