Yes, You need a NVR or a Hybrid solution. I know, that NetAvis, an Austrian/Hungarian company has all things You need. They can do Hybrid (analog via GrabberCard) and/or pure IP solutions. From IP in CIF format up to 5MP. Every channel can be set up for licence plate recognition. The LPR is an option. If You need contacts, let me know!
Regarding triggering:
Most of the cameras themselve have a TriggerInput, where You can directly connect an IR PIR sensor; but with a LPR the better solution was to connect that input to a Inductive Loop in the road. Much better solution, almost False-Alarm-Free.
If You want to have a really good LPR You need to work with IR. I can send You pictures with/without IR, made with a Megapixelcamera, judge Yourself! IR is not so expensive!
Working with Software-MotionDetection is really not a very good solution, but working with a Hardware-MationDetection is ok, but very hard to adjust. You have to come to the installation site several times to eleminate all false-alarm factors. I had once a look at that at an Airport installation - lot of money, but...
You could do it with a LaserScanner from the company SICK. 1 Dimension-scanning, triggering with two areas (logic combinations) - together with LPR... but again, pricing...
Ivan