Here are the EULAs:
Milestone: Their EULA states: "(d) You may permanently transfer all of your rights for this product, provided the recipient agrees to the terms of this EULA."
Network Optix: Their response is it can definitely be done, though going through the original dealer is required. However, their EULA (available via installer only and uploaded here for your review) restricts this altogether: "you shall not nor shall you permit any other party to: ...(iv) externally distribute, sublicense, resell, encumber or otherwise transfer the Software...and more"
Video insight: Their EULA states: "TRANSFER. You may move the Software to a different server." notice it does not say a different customer, or ownership.
Avigilon: EULA available via installer only, and it is a bit ambiguous. It reads: "non-transferable license", and "You may not transfer the rights to the Software to a backup copy unless you transfer all rights to the Software granted in accordance with this agreement." and "You may not unbundled or repackage the Software for distribution, transfer or resale." and finally: "You may not rent, lease, sell, sublicense, assign, lend, resell for profit, distribute, network, or transfer the Software or Your rights in the Software, or authorize any portion of the Software to be copied onto another individual or legal entity’s Computer."
Exacq: Eula only available via installer. limited verbiage on "...not transferrable".
Genetec: Genetec says they too tie to mac address, and you must call sales to transfer ownership - which is allowed. The EULA states: "Except as expressly allowed herein no right to recopy, sell, distribute, license, sub-license..."
Also, all of these mfg have a trial/return period, I would think that the length of time used by Customer A (once activated) will also be taken into account if the request is made to transfer ownership of used license to another customer all together.