Try to read and write it in the TL866C as a "Standard SRAM", either 6164 or 6264. The M48T59Y does have a couple of outputs: /RST, /IRQ - which are NC and CE2 respectively on a JEDEC SRAM, but it could just work. If it isn't recognized, it's likely because of a conflict between its /IRQ output and the expected CE2 input, more specifically that it doesn't respond to CE2.