Does one memory cell take part in different memories?
According to engram theory: Yes.

However, you need more than one cell to encode a memory engram.
The idea is that the combination of cells encodes the memory, not the cells themselves.

I am most familiar with the hippocampus, in which cells participating in the encoding of "concepts" like Jennifer Aniston, Bill Clinton or the Sydney Opera House have been found in humans Quiroga et al. (2008)