For presence, you'll need CUPS. If you have software support on your CUCM system, you can get that for free under the "Jabber for everyone" program. I'm not sure if the free CUPS does enough for Lync presence integration. I think it does, but don't quote me on that!
What do you mean by "audio/video conferences between them" ? If you want to make/receive calls between CUCM & Lync, then in theory you don't need anything extra. You can just setup a SIP trunk between Lync & CUCM. (Cisco seem to be flip-floping over whether you should use a CUBE box between them or not)
If you want video conference calls between CUCM and Lync, in addition to the SIP trunk above, somewhere, you will need a video MCU. Whether this is connected to Lync, CUCM (or even both) will depend on your preference & circumstances. (e.g. are you more comfortable with one system over another ? Which system will have the majority of callers ?)
GTG
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