There is no technological limit that would stop your paid transit providers from announcing your allocations on your behalf.
If you do not have your own ASN, then you can't use the free BGP tunnel. That would be the only technological limitation & policy with regards to the free service (private ASNs need not apply). Or you could pay HE for a tunnel that has them announce the space. Free service only goes so far
to be assigned a rep to talk about a paid tunnel service.