Do you know how the MXP1700 is deployed? Is it a stand alone system, VCS deployment or is it and if how hooked up to your cucm?
I am not aware that there is a SCCP version of the 1700, so its most likely h323 as you said they are not allowing SIP, ...
Even with your older software version the EX60 would be supported with sip:
http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/admin/8_6_1/ccmsys/accm-861-cm/a08video.html
But the EX60 also supports H323, so I would say it should work as a replacement for the 1700.
There are definitely improvements in the h323 protocol on the device, so I would not garantee
it, but its definitely giving a try.
If you are looking into proper video conferencing and especially b2b calls you might want to check
how to upgrade your setup to CUCM10.5 and also look into using sip.
Having a separate CUCM for video might also be something to investigate if your voice guys are to skeptical