Flavio,
On the RM48 (as well as all Hercules Safety Microcontroller) the CHAN0 and CHAN1 are hardwired to INT_REQ0 and INT_REQ1 so they cannot be remapped.
All other CHANx, are after reset by default mapped to there corresponding INT_REQx and can be remapped at will.
These information is visible in the RM48 Datasheet (page 93 section 4.15.2 Interrupt Request Assignments) and TRM (page 502 Figure 15-4 and 15-5)
Concerning your second question, where did you find this timing diagram?
Here is what is stated in the RM48 Datasheet on page 54:
Please let me know if I've answered your questions.