Is S/PDIF out on T60p able to output at a sampling rate higher than 48K?

Supposedly you're using the mini-dock port replicator 2504 as this model has a S/PDIF port (the T60 itself and mini-dock model 2505 lacks the S/PDIF port).

The built-in audio device of the T60 supports for both loudspeakers and s/pdif: 48 Khz, 24 bit (maximum).

You can check it out yourself (in W7):
- Start > Cofiguration panel > choose Sound > Properties

If you're using JRiver Media Center as Audio frontend, set the output-mode at WASAPI-Event Style, set sample rate in this software package at 48 Khz and bitdepth resolution at 32 bit. You will enjoy an excellent musical experience.

If you insist on a higher than 48 Khz sample rate, then you'll need an external USB DAC amplifier such as f.i. FiiO E17 Alpen.