I was busy yesterday, but back :-)
Don't you mean 'I can read the same disks on my 128 as I do on my Kaypro and my Televideo'? Or do these machines all use the same CPU? Isn't the 128 a 6502 (variant), meaning it won't run Z80 binaries?
Others have replied correctly. The C128 also has a Z80 CPU for CP/M mode. I can confirm from first hand knowlege that CP/M binaries are compatability across a wide number of machines, the C128 being one of them.
I remember people touting one of the pluses of MS-DOS was that you could read the same disk on whatever computer was running it, as opposed to CP/M which was meant to be the case, but just wasn't because everyone had their own implementation of CP/M. Microsoft just standardised one variant from the bunch.
When it comes to the floppy disks themselves, it gets a bit tricker, yes. Most CP/M boxes had their own floppy format that other machines usually could not read. The list of various CP/M floppy types is quite long. A Osborne formatted floppy would not work in a Kaypro, for example.
However, this is where the C128 with 1571(and 1581) shines. The 1571 and 1581 are amazing drives. There is a free program called
Juggler that allows C128 CP/M to read and write more than 140 CP/M disk formats. I have used this in the past and it works perfectly. Pretty neat taking my old Televideo Wordstar floppy and running that version of Wordstar on my 128 without a hitch :-D