The only way I have seen this work is to use dial-on-demand routing to drive the backup and time-based access lists to define interesting traffic. Neither backup interface nor dialer watch use access-lists to define the need to dial, so there is no way to control their actualization based on time of day.
Since you need the link to come up regardless of whether or not there is traffic, you will need to use BGP to generate the interesting traffic used to force the dialing. Your IS-IS and DECnet routing traffic must be declared not-interesting or the link will never drop. The technique of using BGP to create interesting traffic on demand is described in a white paper on my web site and in Chapter 5 of my book High Availability Networking with Cisco.
Disclaimer: Response to link outages which do not force the interface down, as may occur on frame relay links unless end-to-end keepalives are used (which I assume you are doing, since you use backup interface), can be delayed by up to one minute because static routes are only updated during per minute processing on Cisco routers unless an interface changes state.
Good luck and have fun!
Vincent C Jones
www.networkingunlimited.com
