cPanel does not modify the permissions of the crontab binary.
Even if your permissions on /var/spool/cron are set to 0700, a normal user in a normal shell should be able to modify and display his own crontab from the command line.
Tested on CentOS 4.6 and FreeBSD 7 (display below is from CentOS, however permissions are the same on the FreeBSD server).
Code:
root@mundane [~]# ls -l /usr/bin/crontab
-rwsr-xr-x 1 root root 82916 Aug 2 2007 /usr/bin/crontab*
root@mundane [~]# ls -l /var/spool/cron
total 36
drwx------ 2 root root 4096 Jul 30 13:15 ./
drwxr-xr-x 17 root root 4096 Mar 2 2007 ../
-rw------- 1 root root 1430 Jul 17 15:40 mailman
-rw------- 1 root mysqlbug 10 Dec 7 2006 mysqlbug
-rw------- 1 root root 496 Jul 30 09:37 root
-rw------- 1 root root 87 Jul 30 2007 standard
-rw------- 1 root abcdee 318 Jul 30 13:15 tramel
root@mundane [~]# su - tramel
tramel@abc.com [~]# echo $SHELL
/bin/bash
tramel@abc.com [~]# crontab -l
MAILTO="tramel"
0 0 * * * echo "Test the 6th" >> /tmp/cptest
0 5 * * * echo "Test the 5th" >> /tmp/cptest
0 4,8,12,22 * * * echo "mimi" >> /dev/null
0 0 * * * echo "hi test me" > /tmp/cptest
0 3 * * * echo "Another test" >> /tmp/cptest
0 3 * * * echo "Test the 4th" >> /dev/null
tramel@abc.com [~]# crontab -e
crontab: installing new crontab
tramel@abc.com [~]# crontab -l
MAILTO="tramel"
0 0 * * * echo "Test the 6th" >> /tmp/cptest
0 5 * * * echo "Test the 5th" >> /tmp/cptest
0 4,8,12,22 * * * echo "mimi" >> /dev/null
0 0 * * * echo "hi test me" > /tmp/cptest
0 3 * * * echo "Another test" >> /tmp/cptest
0 3 * * * echo "Test the 4th" >> /dev/null
0 0 * * * echo "CLI Test" >> /dev/null
tramel@abc.com [~]# logout
If something keeps changing the permissions of /usr/bin/crontab then you need to hunt down what is causing that change.