I notice that some boot disks (namely, tom's rtbt) include this config file as part of their minimal setup but none of the programs invoked by init rc scripts seem to use it (as least it's does't seem to be documented in their man pgs).
Which programs make use of this config file?

/ect/termcap defines the teminal emulation.
It would be used by ssh, telnet, ftp , maybe getty and setty.



Quoting from the termcap man page:
TERMCAP(5) Linux Programmer's Manual TERMCAP(5)

NAME
termcap - terminal capability database

DESCRIPTION
The termcap database is an obsolete facility for describ-
ing the capabilities of character-cell terminals and
printers. It is retained only for capability with old
programs; new ones should use the terminfo(5) database and
associated libraries.

/etc/termcap is an ASCII file (the database master) that
lists the capabilities of many different types of termi-
nals. Programs can read termcap to find the particular
escape codes needed to control the visual attributes of
the terminal actually in use. (Other aspects of the ter-
minal are handled by stty.) The termcap database is
indexed on the TERM environment variable.