IBM have their own TSS......... Atmel TPM's use IBM's TSS when deployed by IBM. NSM TPM's use IBM's TSS when deployed by IBM. Any TPM manufacturer that wants to be considered by IBM will have to make sure their TPM is compliant to IBM's TSS.
This ONLY applies to IBM for PC Manufacturers.
NTRU's TSS is aimed at TPM manufacturers that wish to use a neutral TSS that is not tied to either IBM or Infineon TSSs or application software.