Legacy guys - I like that better than old farts.
I've still got about 30 CS systems in service, but none of them have Caller ID enabled on any of the built-in LS ports. Whenever possible, I sized systems to not use the built-in ports. It's much easier to swap a bad card than to swap the entire chassis.
Having said that, I can't recall any limitations.
Edit: I just noticed you're from the UK. What version software do you have?
From the Help file:
MiVoice Office 250 Release 6.1 allows the decoding of Calling Line Identification (CLID) information in countries which use variations of BT CLIP (British Telecom Calling Line Identification Presentation) signaling on analog trunks. BT CLIP supports the delivery of Caller ID information on analog trunks in the UK, and the standard is commonly known as BT CLIP. BT CLIP is an on-hook capability that provides the user with information about the caller before actually answering a call.
A new trunk Service Type and timer parameters are added in MiVoice Office 250 Database Programming to support BT CLIP. BT CLIP replaces ETSI DTMF Caller ID. When configuring a Loop Start trunk, the Service Type options now include Bellcore FSK Caller ID and British Telecom FSK.
