Privileges for Article CFs


My RT installation uses several groups where each group only has access to a
limited set of queues that they need to see. Now I am creating several
classes of articles, one per queue, to implement a simple Q&A and message
templates. But in order to use articles, I have to define their content
structure through custom fields. The problem I am trying to figure out are
access privileges. For example:

There are groups G1 and G2.
CF1 is a custom field with read/write access from both G1 and G2.
G1 has access to Q1 which has article class AC1. CF1 is applied to AC1.
G2 has access to Q2 which has article class AC2. CF1 is also applied to AC2.

With such configuration, is there any way G1 could access CF1 values that
belong to articles from AC2? G1 has access to see or change CF1 values after
all. Should I rather create CF2, with access only from G2, and use it for
AC2 instead?